This is my first day writing in this platform, iI am learning a lot of things, but iI don´t know how to implement.

Write texting is always important for me, iI like this, mainly when I want relieve my mind.

"Write texts" is a bit unnatural. I think you meant "Writing" in general.

Good Afternoon!!

This is correct, but "Good Afternoon!" is usually a greeting, not an ending.

Text to tTest

titles are usually written with the capitalization rules of title case

This is my first day writing ion this platform, iand I am learning a lot of things, but iI don´'t know how to implement them.

or

This is my first day writing on this platform; I am learning a lot of things, but I don't know how to implement them.

the sentence has three clauses, so they need to "fit" together a certain way

for example, you could also say:

This is my first day writing on this platform, and while/although I am learning a lot of things, I don't know how to implement them.

Writeing texts is always important for me, i. I like this, mainespecially when I want to relieve my mind.

There are three clauses in this sentence as well, and above is another way that they could be written.

"to relieve my mind" sounds a bit unusual, maybe try "when I want to give my mind a break" or "relax my mind"