4 years ago I wanted to play the guitar, so I tried to learn it. I gave up pretty soon and the guitar has been pretty much untouched ever since. Now I want to try again! So my question is: Can i still tune it the right way or does it need special treatment? It's like super out of tune and i don't know if i can save it. Do you guys have any advice on how to handle this?
Your guitar may be just fine. But if you stored it four years with full string tension, it is quite possible that the neck has bowed (at least a little) under the string tension. Hopefully a simple truss rod adjustment can take care of that. So if you are lucky a new set of strings and a truss rod adjustment will put your instrument back in playing condition.
For a better understanding of the action of a truss and a link to a tutorial on how to do it yourself click here: Guitar Set Up and Truss Rod Adjustment
I recommend changing the strings. Even without being played, steel strings will oxidize over time and become weaker and sound dull. You mentioned that you gave up on playing the first time. You did not mention whether your guitar was acoustic or electric but one of the many reasons folks give up on guitar is that steel strings on tender fingers can be very painful in the beginning. Since you are going to want to change the strings anyway and since you have probably not yet developed callouses, you might consider the trick mentioned here which describes a Custom Finger Friendly String Set for Beginning Guitarist.
While you have the strings removed, you should clean and possibly oil the fret board with a light alcohol free lemon oil formulated for guitar fret boards. For some great tips for cleaning your frets and fret board click here: How to clean your guitar's frets and fret board without damaging your instrument
If your guitar was stored in an environment that was less than optimal (too much or too little humidity or extreme temperatures) there might be some damage that would require a protracted rejuvenation process.
Acoustic guitars are very susceptible to damage due to less than optimal atmospheric conditions. Here is a link Humidity and Guitars that tells you more about how humidity can affect an acoustic guitar and the optimal humidity range.
Within this answer to another question on Stack Exchange is some content about proper storage of guitars to minimize any potential damage caused by longer term storage Guitar Storage Options to prevent damage
Hopefully your guitar will play just fine with a new set of strings and some tweaking of the set up (including a possible truss rod adjustment and/or adjustment to the saddle). If not then by all means buy yourself a new guitar and have fun learning to play. It's worth the effort.
You should be able to still tune it. However, After 4 years of not being played or set up, the neck may be warped and the strings might be brittle depending on the environment it was left in (i.e. hot / cold / humid).
You can use a free mobile app like Guitartuna if you don't already have a tuner laying around. Also, you may or may not break a string in the process of tuning (since the strings are quite old). Take your time tuning the guitar. You can start tuning up to the appropriate note and then wrap a couple of fingers under the string and pull out gently to "stretch" the string.
Doing this repeatedly until you've reached the appropriate notes should do the trick.
Additionally, you could tune a half or full step down if you're worried about breaking the strings, or just buy new strings if you do ;).
Carefully pull all the strings off. 4 year old strings may break by themselves.
If the bridge is easy to remove (i.e., Tune-O-Matic styled bridges are held on by string tension), take it off, inspect the neck - if it is straight, don't touch it, if it isn't, straighten it out a little - not all the way. If it is an acoustic, don't touch the bridge, and I'm not overly familiar with their necks, but I believe they are still adjustable.
Get some new strings, put them on, tension them up to your desired tuning, then inspect the neck. If it is still straight, then great, if not, straighten a little more. Then you need to set up the height of the bridge, this is easy, just go on Youtube and there are heaps of videos about it. Basically you want to remove all fowling and buzzing.
Finally, stretch the strings (grab and pull on each one) a bit, and then retune and repeat a few times. And you should be good to go!
Before answering this question it's good to have some insight to some things that can happen to a guitar if left untouched.
A common problem that can occur with untouched guitars is the guitar strings will begin to rust over time and so the guitar will most likely need new strings :).
If the strings are rusted then there is also a chance that the saddle/bridge and tuning knobs of the guitar could be rusted too. If the saddle/bridge and tuning knobs are already rusted then you should look into purchasing new ones.
I have a vintage Fender Acoustic that was untouched for many years and it had a rusted saddle and tuning knobs, after a while the tuning knobs would begin to break off one by one so it is wise to replace anything rusted on a guitar if you still want to keep it in one piece.
Another common problem that can happen to a guitar if unattended to for a long duration is intonation problems. If the guitar has been left in the sun (or even in a hot room) or has been laying in an awkward position, then the guitar neck will begin to bend or twist over time. A bent guitar neck will cause you intonation problems (problems that will make the guitar sound off-pitch as you play higher up the neck). As I have explained in another answer here: weird intonation problem on the highest string
"Can I still tune it the right away or does it need special treatment?"
If the strings aren't so rusted that they will break when tuning then the guitar should tune fine! However, if any of the previously mentioned situations have occurred to your guitar than keeping the guitar intune may be an issue for you.
If your tuning knobs and saddle are rusted then tuning the guitar may not be your best option as your tuning knobs can just snap off if they are heavily rusted (Like what happened to my Fender).
BUT GOOD KNEWS!!!!! My Fender was sitting around untouched for 30 years!!! If your guitar has just been sitting around for only 4 years it should be fine!
Hope this helps :)