Hi Hartte,
Its nice to see you being keen to get a Part 66 Cat A Licence - but its not as easy as you seem to indicate.
From Memory, the Training Syllabus is about 14 Modules and exams. Plus you will need certified work experience sheets showing full systems experience over a given amount of time. This may take two/three years if you can get the study time in and pass the required exams.
I am not aware of the NAA under which you operate in Slovenia, so I can only direct you to the UK CAA website:
ELGD | Personnel Licensing | Safety Regulation
Alternatively, you may want to read another translation of the EASA Part 66 regulations:
European Aviation Safety Agency - easa.europa.eu
For your info I have know some B1/B2 engineers who, as GA Pilots, used to complete their own Check Flights. I haven't seen any as Cat A Mechanics.