Selling a mobile application

Question

Android

Hello, I really need some advice.
A year ago, I wrote my first Android app. But it so happened that from a misunderstanding of many issues, there are many problems in it. There was no time to correct which, and then the understanding came that it was necessary to rewrite from scratch. There was no time for this for a long time.
Now a Korean distributor contacted me and offered to sponsor the adaptation of the application for Korea, and they will take over the distribution there, because. they don't have android market.
But in the end, we agreed on the sale of exclusive rights to the application (now we are arranging the issue of price). This moment suits me perfectly.

But a few questions arose, because I have no experience in this at all:
1. Is it worth bothering and paying taxes on this business. (amount less than 5000$)
2. How to send documents to each other? (Is it necessary to bother and send the originals by mail)

Answer 1

No need.

Answer 2

Can you briefly describe what problems you realized in the end such that it led to the need to rewrite the application?