Hi Yvan,
My sympathy and unfortunately little else that is of practical help, although PLEASE - do persevere:-)
I am a Computer Numpty and although I've tried practically ALL the flight Sims out there since about 1984 AND done a fair bit of real flying I had, until very recently, always returned to my trusty MS Flight Sim 9. It did ALL I wanted to do in flight Simming & as said, I've bought and tried virtually all the OTHERS :-) However, very recently I bought the NEW MSFS and have to say (luckily) have had no real problems...... Clearly there is a steep learning curve - I'm still on that BUT, again I ask that you persevere! It really WILL be worthwhile AND, frankly, I think whatever your problem is - it is not likely to be the Sim. I have all sorts of reasons for thinking that and to be fair, little hard technical evidence - I'm a Computer Numpty remember ;-)
Your problems are likely to be simple settings or similar simple things somewhere - maybe in your Windows or other settings on your Computer. It is very easy, reading some of the Post on Sim Forums, to become disenchanted BUT - almost all the problems people have with getting their MSFS to run are simple.
Keep at it - read all you can and be methodical. You will get there, many thousands - Nay, millions ARE flying and enjoying this Sim...... and there really is a LOT to enjoy!
Good Luck
Phil