Re: hold to to fixed rate or go variable ?
It looks like their variable rates are more than 2% over ECB at the moment, and it's hard to see those margins reducing much any time soon. That means the cost to you of keeping the fixed rate is probably close to €2k a year (and that extra cost will increase as interest rates go down further over this year).
The problem is that it's very difficult to forecast how the broader economy and interest rates will go over the next couple of years, and 18 months is the critical time horizon for you. You could reap the short term advantages (probably to the tune of €4k or so over 18 months - gross saving, will be reduced by lower mortgage interest relief if you're an FTB) by breaking out now... but no matter what, there's very likely to be a longer term cost.
If you're not currently under financial pressure, waiting for the tracker to kick in may be of benefit - I reckon trackers at that margin are unlikely to come back in for many years (if ever), so there's likely to be a substantial long term advantage.
If you are under financial pressure, it might make sense to have the additional money now.
Only you can make that assessment. I'd try to hang in there, but it's not a decision to make lightly either way.