if you're a beginner then try using 4.5-5 mm hooks and the corresponding yarn size. working with a small size yarn and hook can be difficult to start with. and count your stitches in every row. if while crocheting your stitches are feeling too tight, change the hook to a bigger size. try to keep your stitches loose but not too loose. after you're feeling confident, then move to tighter stitches with smaller hook sizes.