Removed python3 hoping to reinstall it, but cannot do it
Solution 1:
You could try aptitude.
Install aptitude like this:
sudo apt install aptitude
Or if that didn't work, download the aptitude .deb
package from here for 64 bit and install it like this:
sudo dpkg -i aptitude_0.8.10-6ubuntu1_amd64.deb
Or install the downloaded package by double clicking it so it opens in the GUI package manager (ubuntu-software) and install it from there.
After that, nstall python3 like this:
sudo aptitude install python3
Aptitude is good at resolving dependencies and will most likely succeed in your case.