I've been learning to play the violin for 4 years. I always struggle with reading new music piece, it takes me quite a while to fully understand it, by that I mean to actually know the rhythm and become acquainted with the techniques performed in that piece. How can I improve the sight-reading speed and how to correctly and quickly analyze a new music piece? I always find it hard to identify the beat and usually mess up with notes' length.
Make sure you can sing it before you try to play it. Or, if it's outside your vocal range, sing it internally. Tap out the rhythm. Then, when you're clear in your head what it SHOULD sound like, start practicing it, section by section, as slowly as is necessary to get it right. This is the important part. Play as slowly as is necessary to get it right. If you fumble, you're trying to go too fast.