I am medium , i dont take any protein shakes.1. If you cant run fast than take it easy run slow then after couple of week running slowly then try to build the speed up dont rush. Are you fat or medium or skinny?
If you skinny you dont even need to run
2. Yes you will get muscles pain but you have to take it easy.
Again dont rush, start with very light weight then build it up.
are you taking any protein shakes?