oh =[ a few people told me that its bad after a working with weights... told me i should keep muscles tense; is that true?
Only way I could see it being bad for you is that steam/sauna room is going to lower your blood pressure (heat does that).
I personally don't have a problem with heat but some may. The only thing I could see screwing you up is your blood pressure will drop which may lead to fainting.
I rarely, if ever, get into a sauna or steam room after exercising. Just doesn't appeal to me... I'm already hot/sweaty and don't need to further that along any! I do get into a whirlpool occasionally but it is typically at night after all the exercise has been done for the day.
You should get some carbs and protein (and some glutamine) in you within an hour of training. This is when you are going to maximize the nutritional benefits and give your muscles what it needs when it needs it.