To become a better singer, you need to focus on your breath and the proper sing posture first. Make sure that each and every day you practice and exercise severally. As you practice, do not strain your voice because this may damage you vocal chords.
There are a different variety of things you could try... but one of my favourites (i know it sounds stupid) but if you actually lay down in a straight form it will help your singing experience! because it spreads your diafram further apart giving your vocals and throat the perfect room it needs to perfect such amazing music! Trust me it might not work right away but if you do about 10 minutes a day for 3 weeks it should improve your vocal chords!
Well im an alright singer, cuz i can hit high notes, but what you should do is record yourself singing and see where u struggle the most, high notes, low notes, mid notes, key, tune, and etc. just sing a lot and always try new things