Assalamu alaykum Ustadh How do I know that my heart is not dead and there is still some light in it? I believe that I'm a bad Muslim and that my heart is dead and no longer alive. I also very often think that I do my deeds for the People instead of Allah, ta'ala.

It seems to me that this is a case of compulsive disorder that we call waswas. You should ignore these thoughts altogether and continue upon the goodness that you are doing. If you want some leniency of the heart, then it is by the remembrance of Allah Subhanahu wa ta'ala. You can study our Righteous Muslim Program, as it brings, Insha'Allah, leniency to the heart and issues that make the heart more lenient. Also, if you think that you have a psychological disorder, then the first thing you should do is go to the people of the field (like psychiatrists) and see if you need their help.