Front window freezes from the inside to

Hallows, since last winter in Frost big problems with the inside frozen windshield of my variant (’92), therefore I put in a dehumidifier (ceresit) and in Frost covered the windshield nicely. Unfortunately helped. In December 03 I did an 8-hour tour and nicely heated. After that there were no major problems with the first minus degrees. However, I found out during carpet vacuuming that the floor is quite damp. Rubber mat –> Carpet protection (as standard?) –> Carpet is my order. Now the carpet at the front is re and li and the back is just quite damp. It doesn’t “smack” straight, but when driving over the carpet, the hand is already a little damp. In December I was still in the washing machine and did not notice any water entry from above. Does anyone know the situation? Can it be that the water comes in from below? How can leaks be detected? I am grateful for all ideas and tips. Greetings muellers