The relevant word is "possibility" of a 6.5% return over six years. So your actual return after 6 years might be €25,000 or might be more, up to the 6.5% per year cap.
This sounds like a tracker bond of some sort. You're probably locking up your money with no access for six years.
You'd have to post more detail on what it tracks, participation rate and other technical details before you could get a meaninful answer as to whether it's good bad or indifferent.
You'd also have to post details on your own requirements from this lump sum (willingness to lock it up for 6 years with no access, requirement for income?) and attitude towards risk you're willing to take with it.