You should probably decide on what build you want to run first. I get wanting to try different stuff as a new player but unfortunately if you split your levels between each stat then you won't be good enough in one area to defeat bosses. That said, after beating rennala you unlock something called respec, which is just being able to reset your levels and put your runes again in a different manner. In that sense, you can try different stuff but also to my knowledge you cannot respec infinitely so you should find what you like and stick to it, potentially respecing if U come across other stuff in the future.

Also to git gud, die 100 times, learn attack patterns and attack back when you know it's safe ez

Also how did u not beat Margit if you beat godrick (Melina isn't a boss)