Removing untrusted certificate

Hello,

Each time I open my iPhone, I get a pop-up about that my iPhone does not trust a certificate.

It does not show anywhere that I have it installed and I cannot manually trust it. Does anyone know how to fix this?

I don’t have any profiles or an option for it.

I saw a kind person reacting the same comment on lots of peoples question (who had the same problem), I tried to do what the man said but no prevail.

Sorry for the language difference but I hope that does not make it any difficult for a problem solve.

Kind regards.