Here are three strategies:
1/3 Ask them to sign a contract for month May
Here’s an example of a contract to print:
Agreement between ……… and ……….
I’m happy to help you learn a language by having one conversation per week, leading to 4 per month.
[ ] [ ] [ ] [ ]
Your friend, ……….
2/3 Schedule a weekly time together
It’s harder to run away from a agreed time and date. Spontaneity is nice, but you may always feel the “now is not the right time” excuse. Or maybe you’re trying to protect your partner. Be clear about how much time you want to schedule for the learning. Usually 30-40 minutes is enough, and it will be easier to keep it up when you also agree on this.
3/3 Offer to cook for them on a certain day
Cook something from your home country and that way invite them for. Be sure to always have 3 recipes you really now how to make well. That way you can say “shall I make pancakes on Thursday again”, to create a habit of practicing.