When writing a story, and there is action, then the person reflects on the action, how is that translation from action to thought written?

Simply?

John stepped out in the yard. He saw a basketball lying on the walkway. He picked it up, noting the mud on the orange surface. How did this get over the wall and into the yard? Nobody had a basketball hoop in the neighborhood. Why was it here?

It’s not a “translation” it’s a TRANSITION.

In 3rd person viewpoint, it’s cause / effect — action / reaction. The example above is action, observation, response. The internalization is context, then speculation.

Even as you scale complexity it’s pretty much the same.

It’s not always call and response, it can be ping-pong within the passage itself.

Clutching his sister, empty of mana, heart pounding and lungs like spikes in his chest, Dae stared up at the Kriar insurgent as the gold-skinned sentient's finger twitched to fire again. He had nothing, contingencies scrambled, off-balance, no cover, no viable weapon. Fear for him, fear for Kharabelle, searing anger at being suckered into the trap. They intended to bait the enemy away, but it had been the enemy baiting them.

Heart thumps at the speed of a blinking eye. Not enough air. What to do. What?

Noise.

Chaos.

Smoke.

Stench.

Dae fixed on the kayyar's implacable dead black eyes, legs and arms steady, the weapon barrel poised in absolute stillness, the flickering illumination of torch and lantern light glinting off the metal. The outverser felt no doubt or hesitation, murder came easy for them.

Helpless anger, frustration, and a desire to live exploded behind Dae's eyes. He glared at the gold-skin hoping to at least curse him in the afterlife. He couldn't even lift a pebble with telekinesis. Don't just freeze. Do--

Something!