Please can anyone help with this kitchen problem?!

[tywn]

There’s black mould all around the sink where it sits under the counter. It’s a ceramic sink, don’t know if that makes a difference. All where the overflow is is black and also the bit between the counter and the sink if that makes any sense. I’ve cleaned it and it literally comes back within days?!

You need mould and mildew remover to get rid of it, then you must keep the areas dry.
If it's under the sink then it's possible that the seal around the sink itself is leaking and needs to be redone. You may be able to do this yourself, if you're feeling brave!

HG Mould remover is good. There’s probably some other mould in the room or air that needs removing too. We had to get an extractor and open the widows for all cooking to get rid of the mould we had even though it had been treated.