I want to learn polish.

I am planning to go poland.For that reason need to learn polish.

I want to learn Polish, because I am planning to go to Poland. That's why I want to learn Polish.

Notes:

1. Countries and their languages (国、語) always take a capital letter (c - C).

2. You can combine the sentences by explaining why you are learning the language. You can compare "because" to から、が、etc...

3. You can use 'why' after "that's" to explain your reason. No need to use "For that reason"

I want to learn polish.

I am planning to go to Poland.(For that reason) i think it's better to say:So i need to learn polish.

I want to learn polish.

I am planning to go to Poland, that's why I need to learn polish.

I want to learn Polish.

I am planning to go to Poland, so for that reason I need to learn Polish.