Transmission/engine communication issues

Hello there and thank you for your help in advance.

When engaging gear on my car the engine RPM goes up instead of down, I think the engine does not know the transmission is in gear which as you know it causes many other issues not to mention the car jumps when in gear and that puts pressure on many other components.
If you think it is transmission sensor or any other issue could you please show me where it is located and a picture of it would be nice?
Best regards and thank you again.