My Tenant Doesn't Want To Return My Deposit

Location: México City

When I rented four years ago with this tenant he told me that because I didn't had a person to be my cosigner I could pay 2 deposits, usually this cosigner works as a guarantor to ensure that you pay, not sure if this is commonplace in other countries but it is quite common in Mexico.

After four years when I told him that I wanted to move he said that he wanted to send a family member to check on the state of the department, this person never came by but he said that after a chat with him both agreed that they won't return my deposit.

For this the department had many issues that were already there (for example the counters in the kitchen where made of bad quality compressed wood and they drop splinters when opened or closed and from the moment that I moved in he told me that those were bad and he wanted to change them but never did so). And he mentioned that those where on me as well.

The two main things that got worse on my time there where that the bathroom walls got a fungy due to the lack of ventilation as the bathroom had no windows, when I removed the fungus it died but left a stain and one closet drawer that lost its handle, at most and I'm being generous these fixes would be worth 1 quarter of what he owes to me.

When I noted that he mentioned that in case that I made all of the repairs he should return me only one deposit and that the other one was paid for him to ignore the fact that I didn't had a cosigner and that that money won't be returned anyway.

For context the full amount is $800, I know in some parts of the world is not much but I was laid off recently and really need that money.

I have screenshots where he asked me for the double deposit and a screenshot that shows that I already paid them but in the contract ther is no mention of the deposit