My Fourth Day of Intense Study

I learnted around 30 new words and I'm goingnna to use it when I will talking with my brother.

"Learnt" seems more formal. "I'm gonna" is more informal, for formal or academic contexts, use "I am going to", or "I intend to" is an even more formal alternative.

I want to saytalk about my grammar.

I suppose my grammar skills are around Elementary, but I should to learn Advanced grammar for a progress.

Today I also watched "The 100".

I wanted to tellalk about it but I am not sure what I can say.

But for now I can only pass all my time by watching the movie :)

Today is the fourth day of my little challenge: I am going to improve my English skills from B1 to C1 in 60 days.

I learnt around 30 new words, and I going to use ithem when I will talking with my brother.

I think above is the least modified version.

The comma is needed to separate the two clauses.

Also, "it" should be "them" because it refers to "new words."

"when I talk" implies a future activity, so "will" is not needed here. That said, it would normally say "will be talking" or just "when talking"

Also, "learned" is another common way to spell it.

Another possible revision: I learnt around 30 new words that I'll use when talking with my brother.

I want to saytalk about my grammar.

If you use "say," the reader will expect to see something like this:

I want to say about my grammar that_________.

I suppose my grammar skills are around Eelementary, but level, so I should to learn Aadvanced grammar for amore progress.

The first part "I suppose my grammar skills around elementary" is missing a verb

"for a progress" sounds unusual. "progress" is a synonym for "advancement" or "growth," so maybe it is easier to see why "for a growth" or "for an advancement" doesn't work.

You could also say:

I suppose I have elementary grammar skills, so I should learn advanced skills to progress more.

I wanted to tell about it but I am not sure what I can say.

"what I can" needs something else. What I can ________.

If you don't want to add more, you could say "I am not sure that I can."

But fFor now, I can only pass all my time by watching the movie :)

"but" like it is used here is used to conjoin two clauses, and it usually comes after the first clause.

"all my time" sounds overly specific

Today I was lazy because I started later than I had planned.

You would use "had planned" here because "started" is already in the past, and the planning took place before that time in the past.

I learnt around 30 new words, and I am going to use ithem when I will talking withtalk to my brother.

I want to saytalk about my grammar.

I suppose my grammar skills are around Eelementary, but I should to learn Aadvanced grammar for amore progress.

I wanted to tellalk about it, but I am not sure what I can say.

But for now, I can only pass allspend my time by watching the movieshow :)

Fourth Day of Intense Study

Even better: The Fourth Day of Intense Study / My Fourth Day of Intense Study

I learnt around 30 new words, and I am going to use ithem when I will talking withtalk to my brother.

Words = plural --> "them"
It's generally ok to say "talk with," but "talk to" is more natural/common.

I want to saytalk about my grammar.

"To talk" is the general act of talking/speaking. "To say" is when you are going to make a specific statement. "I want to talk to you today about lions" -> I am announcing that I will speak about lions, in general. "I want to say that I think lions are really cool" -> I announce that I have a specific statement to make, and I make it immediately.

I suppose my grammar skills are around Eelementary-level, but I should to learn Aadvanced grammar for ato make progress.

No need to capitalize elementary and advanced.

Today, I also watched "The 100"."

Punctuation goes inside the ending quotation mark.

I wanted to tell you about it, but I am not sure what I can say.

You need the complement, tell (someone). Here, you can say "tell you," where you = the reader(s).

Maybe tomorrow I willcan collect my thoughts and do it.

Since this is speaking more about your possibility to do something (there is doubt involved), "can" is a better choice than "will"

But for now, I can only pass all my time by watching the movie. :)