I know that there is Chipmixer which sends me chips that was created in the past. I like the principle of this site, but how can I be sure, that they really don`t save the data, and if the site will be hacked and everything revealed, the chips can be connected to me?
IIRC, chipmixer does not store sessions for longer than 48 hours, so in case of a hack or breach, your data is not available to be leaked.
For extra privacy, you can use it over the For browser and use a .onion address to access the website.
It became a week but you can destroy your data whenever you want on the site (eg once you've received your funds).
OP is there a reason you want to donate the funds? There might be ways it becomes easier to help them if you live in that country (potentially even while remaining anonymous).
ChipMixer definitely have the strongest recommendation for a centralised mixing service here and it's unlikely logs are kept but funds you send to them will look like they've been mixed (I'm not sure if this is a problem though on your end if they kyc exchange is based in your country it might be).
There might also be the option, if you contact the charity themselves, that they'll be able to offer you advice on how best to donate to hide your funds (maybe buying things for them over tor while hiding your details or by sending them smaller amounts of crypto - still mixed - but harder to trace).
There might also be ways you can donate on other systems such as the lightning network, which is a lot harder to trace.