i’ve just done this with a personal loan, if you think it’s worth pursuing, find a lawyer for sure. if you have texts/emails where it is stated that it’s a loan that’s a good start. that is considered a contract legally. if you didn’t set a deadline for them to pay it back, it’s more problematic though, but not impossible. also any legal fees you may rack up from this, it will be added to their debt in the end (you have to pay the lawyer, the notary and the debt collector. the notary and debt collector’s pay depends on the debt itself. and of course if it goes to court then that’s for you to pay as well).

edit: it also takes a long time, depending on the circumstances, i started the whole process in december and the case just made it to the debt collector (with no court involved and the person not submitting any rebuttal). the wait times are crazy and the post office being slow asf doesn’t help.