I suggest that you write to the lender, explaining that
- you have recently become unemployed,
- your financial circumstances are difficult at the moment,
- your income is less than it was.
Tell them that you are going to pay them €xxx per week from now on and that this is the most that you can pay.
You cannot expect them to be happy about this, and they may make threats but I think that they will not actually do anything.
Presumably your income is weekly so I suggest paying weekly, can you afford €10, I think that is realistic.
And there is no need to worry about this, there is no reason to be stressed here.