Android phone hacking into my Wifi

Hey everybody Someone keeps entering my wifi, although I changed its name and password multiple times. I can see the name of the android which is the initial name, smth like android-638cf639cj397.

So I was wondering if there is any way I could find out who that guy is...?

I dont know what I should use as password, my password is pretty long, had nothing to do with my wifis name, it consists of capital letters and normal letters as well as numbers.

Any tips on how to make my wifi more secure?

Thank you in advance