Q:

Best way to get my money back from a friend having family problems

Back in 2018, in June, a friend working in the UK (let’s call him Dave), asked me to lend him money because he has “family problems” mentioning he will return them by August, 2018.
Things did not go as expected: he divorced his wife, and could not return the money by August, 2018. Not only that, but he got the vice of gambling (I do hope he gave up on that by now).
Every time he set another deadline for sending me the money, but could not do it because of new problems.
The total sum to return is 10k EUR. 
Currently he has girlfriend, and they sent me €500, saying that they will try to do that every week. That happened only once tho.
Now Dave has to pay lawyers to solve some problem related to his son, he has to pay invoices, car tickets, car rates etc.
So, I am in the situation of having a friend who can’t return the money now, he and his girlfriend ask me for patience, and I don’t see any plan from them to return the money.
Dave works very hard, getting around €1000 / week, and I have enough money, not really depending on the money I have to get from him.
While I can wait more, I would like to know that’s the best way to make a good plan for them to return the money.
I don’t want to use force, because I can imagine he has a hard time already, and the worst thing would be to fall in depression or even worse things.
What can I do? How should I communicate with him to return the money? Would it be an option to contact his family (brothers and parents) to make things more transparent for everyone (I do have the feeling he hides some things from me because he does not want me to talk to her brothers and parents)?
Taking legal steps at this point is too early I believe. That would make him even more stressed. 
Given the political changes in the UK I am also afraid that things can get even worse for Dave: he is not UK citizen, the GBP/EUR rate may change in his favor or not etc.
We did not sign a contract — I only have the discussion history (Facebook Messenger) and the TransferWise transactions. 

A:

As a general rule of thumb, when lending anything to a friend or colleague, never lend more than you would be willing to give as a gift.  If it gets repaid, that's great. If it doesn't, chalk it up to the cost of learning a lesson about this person's character, and never lend anything to them again.
In Dave's case, your comments indicate that you still consider him a friend, and that you care about his situation and well-being.
I'd suggest that you choose one of these future paths for your own well-being and peace of mind:

Continue being Dave's friend, but accept that you'll likely never get your money back.  Your friendship is worth more than the money you lost.
Stop being Dave's friend, and count the loss as a valuable life experience.
Stop being Dave's friend, and treat his debt like a business situation, taking legal steps to reclaim what you can.  Do not take on any guilt about this decision; Dave is in the wrong, not you. (In the last year did he and his girlfriend ever eat at a fancy restaurant, take in a play, go out drinking with others, etc.?  Every time, it was paid for with your money.)

Whatever the case, as a favour to both of you, please have enough sense to never lend him another penny.

A:

I assume the goal here is for both he and you to feel some progress is being made toward repaying the loan, even if in practice very little is done towards achieving the final goal of total repayment. Realistically, you may need to write this off as uncollectible, depending on your actual relationship with Dave.
Half his salary (let's assume his girlfriend is not obligated to support him or his debt in any way) was an unreasonable payment plan. Some smaller amount, such as €50/week or less, may be more reasonable. Though it would take quite a while to repay €10,000 at that rate, it would be something, and could be increased if his circumstances improve.

A:

So, I am in the situation of having a friend who can’t return the money now, he and his girlfriend ask me for patience, and I don’t see any plan from them to return the money.

I would just let it go and write it off.
Dave can't pay you back or he would have addressed it already
The fact that you can't cite a reason for the loan (i.e. Dave broke his leg and had medical bills) is a hallmark of someone who cannot manage money. A very common scenario is that Dave was probably simply servicing his debt when he had something happen that he couldn't pay with more debt, or he needed to pay off one debt to take on more debt. Reminders and payment plans are nice for responsible people. Dave may not be in that category.
You won't be able to collect without reminders
Even if you're friendly ("Hey Dave, about that €10k..."), you're now just another bill collector to Dave, probably in an ocean of bill collectors. Dave will either placate you, regale you with sob stories, or pay you small amounts inconsistently (Hence your €500, followed by months of silence).
Even if you care nothing for Dave, the time and effort to get money back just isn't worth your time. If Dave brings it up, talk honestly with him, expressing concerns for his situation. Remember that if Dave does bring it up he has some concern for your relationship. If you kill that, the chances you see anything diminish greatly.
In some rare cases, people like this will not rest until you are repaid. Dave paying you something when he can is better than nothing at all. I've had people I  "loaned" money to (without any real expectations of repayment) do things out of their way to aid me.

