Flat battery,alternator, starter - problems

[ArtisUK]

Hello everyone.. Im new in this forum
Im looking for some help and found this forum...
Hope you guys can help me.

Car is 120d hatchback 2005 year

So everything started Friday was driving to shop from garage. In garage my battery went flat so did jumpstart everything was fine.
After shop i was driving home like 7 min drive... 1st my radio started to act weird looked like loose of electricity switched off by itself then on then lights in screen went blur my first thought was alternator has gone so straight a way went back to garage stopped at garage and my car died. while was driving to garage i had all possible light on dashbord also AIRBAG light came up.
Tried to jumpstart from battery nothing, starter wont turn just those 2 clicks. tried from front to jumpstart and it did. scanned car with scanner errors was safety terminal and alternator my mechanic said that tomorrow 1 electric guy will check it. That electric guy checked alternator and said its fully working.
Later next day i bought new battery and changed alternator ''just in case'' still cant start car when pressing button to start you can only hear 2 clicks from starter but starter has been changed like 3 weeks ago so i think it cant be starter problems( also i think if it would be starter then it wont work also if jumpstart from front ? ) next i changed positive cable and that box for battery(whole gadget) still same problem
erased all errors also airbag but alternator still stays (just jumps back after erase )
Was reading a lot about this safety terminal for battery but even after changing that whole gadget still doesn't start.
Have checked all fuses everything fine tried to change this blue relay still same problem..
Everything in car working except that cant start.
Sorry for long story just wanted to write everything as it happened.
Hope you guys have heard or had something similar and can help me ....

Thanks in advance,
Artis

Edited by ArtisUK on Sunday 3rd March 19:06