Basic knowledge of C++ and Signals&Slots in Qt is a good beginning. You can learn the rest on the way while fixing bugs.
Take a look at the junior jobs at https://community.kde.org/KDE/Junior_Jobs . Another way (which i personally prefer) to find bugs is to use KDE Software (lets say Krita, Gwenview etc) and find small things to fix.
Hi, I am Hrittik from UEM Kolkata. I tried to go through the kde bugs but had no idea how to fix them. I know c++ and currently learning qt. How much c++ and qt do I need to know to be able to solve the bugs. Thanks for your time.