What could I do to boost the productivity from a slow thinker?

I am feeling drained and exhausted. I recently became a middle manager because my company is opening a branch in another country, and I am managing the developer there.

What really drains my energy is that I work remotely with the developer in that branch. For every task design and every word I say, I have to be well-prepared and stay calm. The main issue is that one of the developers there is a very slow thinker. I allowed them to use an AI agent, thinking it would speed up their coding process, but it is taking longer than expected.

The task already includes detailed user stories and acceptance criteria. I genuinely cannot figure out why a simple task is taking such a long time.

I will ask the developer about it later, but before speaking with him, I want to understand the situation better myself.

You might wonder what the task is, right?

It’s simply removing one option from a select box and applying the same action to a checkbox.

[Select box] [Date filter] [Checkbox]

So my question is, in this situation, what could I do to boost the productivity from a slow thinker?