hey sourav

it is a very broad topic so i cannot cover it whole here . you will need a good planning and good educational background for this . make the list of the recquired documents and things . there are some videos of indian students in germany pursuing phd on youtube so watch them also .i know about a organisation which you can believe named DAAD which will be quite helpful for you .checkout this organisation

https://www.daad.de/en/

there are some private groups too which will provide you help in studying in germany but be very carefull with them as most of them are just for money and can cause problems in future.

be very clear with your plan and don't miss anything .

best wishes