Installation and Path-Problems with Ubuntu 20.04

Dear all, I posted some problems in the last days which it seems all belong together

I first installed everything via package source, and apt-get (since I am a newb when it comes to more complicated stuff in linux)
But I had some problems with Code which was working before and works on other pcs

Afterwards I compilled it on my own via this explanation and in the end I installed it via anaconda like christopher told me herehere (I think)

Still, ngsolve has problems, now no longer at the just mentioned place of my code but much earlier. It seems that my paths do not fit at all was explained to me now.

code michael@michael-ThinkPad-X1-Carbon-5th:~$ echo $PYTHONPATH

(base) michael@michael-ThinkPad-X1-Carbon-5th:~$ echo $PATH

Can someone explain me how to set every path correct permanently, I had problems with that already herehere? And any idea why it didn’t work from the beginning?
I am also fine in deleting everything, python, anaconda, ngsolve, and reinstalling it, if someone knows which packages to remove

Thanks to you all for your never ending support and have a nice weekend