Question edited for clarity, and change the Spanish gentleman 'Manuel', to the instruction book 'manual'.
These crooks charge for a manual to their own products!
When I can’t figure out something I just always look for a YouTube video tutorial to help me- Even a turnip can do that! ??I found a couple of tutorials for you- good luck!!
Basic Introduction to Electronic Typwriters- https://youtu.be/Zl3oaQX6yF8
There may be 2 or more cables from the keyboard connected to the main circuit board. If you have these ribbon cables, they will have to be disconnected and cleaned. Look for a plastic clamp that must be lifted to remove the cables. The cover must be removed to access these connections.