pogłębiać in English:

Kelsier's smile deepened

We have to deepen the well.

The mystery deepened when a newspaper published photographs of the couple.

The longer they knew each other, the more their love deepened.

it will deepen your relationships in ways you probably can’t yet imagine.

The details you would learn about her end would only deepen your grief.

He went to Britain to deepen his knowledge of the culture.