There are many tricks, mnemonics and videos to learn the keys and signatures.
The fastest and easiest way will be:
Write with a non-permanent pen the names F,B♭,E♭,A♭,D♭, on your fingers 1,2,3,4,5,
Write with a non-permanent pen the names G,D,A,E,B, on your fingers 1,2,3,4,5,
How to find the numbers of sharps and flats in minor keys?
Number of sharps:
Number of flats:
How finding the numbers of sharps and flats in major keys?
There are several mnemonics to memorize the circle ...
My advice is:
First mind on the top of the circle we have (0#/0♭)
on the left F=1b, on the right G=1#, (the 3 chords we need to play the cadence I-IV-V-I -> C,F,G,C).
At “6 o’clock” we have the enharmonic equivalent F#/Gb -> 6#/6♭.
how to find the numbers of the others scales and keys?
mind the word BEAD:
reading the circle counter-clock-wise starting at "12 o'clock" with C=0♭:
B♭,E♭,A♭,D♭ => 2♭,3♭,4♭,5♭ and: G♭->6♭
starting at 6 o'clock: F# =6#
B,E,A,D => 5#,4#,3#,2# and G->1#
there are several other verses of words beginning with the letters of the names of scales and keys that you can tell and count the sharps and flags on your fingers, like:
Father Christmas gives Dad an electric blanket. (flats)
Fuzzy Cats Get Dirty After Every Bath (flats)
Blanket explodes and Dad gets cold feet. (Circle of 5ths from B to F)
btw: there are lots of youtube videos teaching the circle of 5ths:
My further advice is (also for beginners!):
Try to develop all scales by playing and writing the tetra-chords and you will not only memorize the stuff, but will really learn and understand it!
Then draw yourself a circle of fifths, look at it with full concentration, make a fotograph of it with your mind, close your eyes and try to see it inside: the clock from 1 to 6 o'clock, the name of keys/scales, the key signature and the name of keys: G,A,D,E,F# and then do the same with the flats.
If you're interested in more about the circle of fifths,
this is a good video: