I am from Warsaw, Poland. I have been learning English for some time. Now I found it very helpful to watch the sitcoms. Apart from the sense of humor which is surprisingly close to the Polish one You can learn a lot especially if there is a lot of talking. Unfortunately I am not that good to catch all that is said in the film. There are dedicated web sites to some popular sitcoms like Only Fools and Horses where you can find the scripts. Scripts for most of the sitcoms however are not to be find. Actually I am looking for scripts of the following series
1. Going Straight
2. Steptoe and Son
3. Till Death Us Do Apart
Can anyone help me with that ?

Rather than scripts, have you thought about subtitles? That way you see and read what is said. You can watch with the sound off, and should you wish to confirm something e.g. pronunciation, you can go back with the volume turned up/
Most recent DVD releases and Netflix have subtitles.

As a native speaker, I prefer subtitles on too in case there is a strange phrase or I missed something.
It also helps with spelling - English is a strange and curious language to learn the spelling for, although beware of Netflix as their subtitles are littered with errors including grammatical mistakes.

Definitely agree on the subtitles. Comedies from the North and the South of England vary in their dialect and I've found the old 888 page valuable on many occasions to understand certain lines and words.