Does smoking makes you act stupid or different?

That depends what you are smoking and how it affects you.

Cannabis does cause changes. Different strains of marijuana can be of different strengths. Starting use at a young age has been shown to reduce IQ. Long term use can lead to psychoses.

Tobacco is addictive and people crave the nicotine fix and will take extra breaks during work to smoke. I do not know about any studies showing tobacco use making someone stupid, but starting smoking and continuing to do so isn't the smartest thing in the world.