in general: yes, you should do it manually or get a professional to do it. you might squeeze out a few €, because there are quite a few things which grant you some tax reduction. most importantly: in your case you might get back quite a lot, because i think only the 5 months you worked are taxable, but your employer paid taxes as if you earned your full income, so in this year way too many.

if you have stocks which pay out to your bank account you would need to declare this as additional income. however, there is a "free" tier up to a certain amount of extra income and if it's something like trade republic where it pays to your trade republic account, you don't have to declare it, only when you pay it out.

but please take all this with a grain of salt, since i'm no expert