“I'll take this one.”
I'll take … announces a buying decision in a store. It uses the same pattern as I'll take it. in A1-40.
A1-51 / CEFR A1 / EPISODE 51
Asking the price and recipient of a gift
SceneAt a souvenir shop.

WORDS & CONTEXT
I'll take … announces a buying decision in a store. It uses the same pattern as I'll take it. in A1-40.
Here to remember ... expresses purpose: in order to remember something. Tina wants to give Frank a souvenir so he can remember their trip together.
Both uses of it refer to the souvenir Tina chose. Keep it here means to treasure a gift and hold on to it. Visit is normally used for people or places, but Frank treats the souvenir like a living thing and tells Tina she can come and visit it. This is a small punchline, and it also hints that he wants Tina to come and see him again. In A1-59, we learn that Frank has been carrying the souvenir with him all along.