I did not have time until now to write an update but here it is:
middle chainring was mounted flipped; it considerably improved after I changed it.

Gear has however not been working 100% after i flipped back the chainring (i had actually taken down the whole thing just because there were some issues before); amongst others, the chain would by itself fall from the middle ring to the smallest ring when I had the largest cog in the cassette (I know you should not have the chain like that, but some times it is just where you find yourself to be when you hit a hill, especially in a trail) AND the chain would jam when I descended towards the smallest cogs in the cassette while at the some time changing from the middle to the smallest chainring front.

That was due to a mix of: chainrings being slightly belt, (possibly) excessively steep body angle in the derailleur (meaning it was too close to the cogs) and possibly also some teeth in the chainrings being bent. I have tried to address all of those but have not extensively texted the bike yet... by the way the previous owner should have had the some problem because the paint all around the chainrings and on the front of the chainstays is all gone