How would you protect your deposit with a partner?

Me (27F) and my partner (28M) are looking to buy our first apartment together. He’s been renting since he was 17/18, while I’ve lived at home up until now, so I’ve managed to save up quite a sizeable deposit - around 230K, while he has around 5K saved. We will be using my money for a deposit, but I’m not sure how to go about protecting this should things go south? Originally I thought it would be as easy to just say if we split I get my deposit back and then split the rest, but then I think about how much I could’ve been earning on that money + inflation and what not, and think that maybe it would be better to get a % back? E.g my 230K is exactly 30% of the apartment we’re planning to buy. In the future if we split, I would receive 30% of the sale of the apartment first, and then we split the rest?
I’m not sure, what has everyone else done in this situation?