Track and field is verylots of fun! Track and field is lots of fun!

"Fun" is a noun, not an adjective, so you can't say "very" before it. I remember my mother correcting me on this point when I was a child. I would say "It was so fun" and she would say "So *much* fun."

I joined a track and field high school club activity 1 years ago. I joined a track and field high school club 1 year ago.

I joined a track and field high school club activity 1 years ago. I joined a track and field high school club 1 years ago.

If you wanted to say the first time you did an activity with this club the sentence would be "I joined my first track and field high school club activity 1 year ago."

I joined a track and field high school club activity 1one years ago. I joined a track and field high school club activity one year ago.

It's better to spell out single-digit numbers as words ("one", "two", ... "nine") unless there's a good reason to write them as digits.

I joined a track and field high school club activity 1 years ago. I joined a track and field high school club activity 1 year ago.

I’ve liked running forsince I was a children. I’ve liked running since I was a child.

I have liked running forsince I was a children. I have liked running since I was a child.

Since it was in the past your sentence needs to be in the past tense.

I've liked running forever since I was a children. I've liked running ever since I was a child.

I like running for I was children. I like running.

Now I am doing an 800m competition. Now I am doing an 800m competition.

Now II am now doing an 800m competition. I am now doing an 800m competition.

You say "an" instead of "a" before 800m since 800 starts with a vowel (aeiou) when speaking aloud (Eight-Hundered). Alternative sentence which would also be correct: "Now I am doing an 800m competition."

Now I'm doing 800m competitions. Now I'm doing 800m competitions.

Now I doingam participating in an 800 m competition. Now I am participating in an 800 m competition.

It is a very hard and fun distance. It is a very hard and fun distance.

It is a very hard and fun distance. It is a very hard and fun distance.

Personally I would also replace "and" with "but" as usually hard does not mean fun

It is a very hard and fun distance to run, but a lot of fun. It is a very hard distance to run, but a lot of fun.

It is a very hard and fun distance. It is a very hard and fun distance.

How longWhat distance do you like to distance onrun for Track and field? What distance do you like to run for Track and field?

How longWhat distance do you like to distance on Trun for track and field? What distance do you like to run for track and field?

"How long do you like to" needs to be followed up with an action and "distance" is not an action. Because of this the sentence structure should be changed. A word usually does not have a capital letter in the middle of the sentence unless it's a name, month, weekday and some other exceptions.

How longWhat distance do you like to distance orun in Ttrack and field? What distance do you like to run in track and field?

How long do you like to distance orun in Ttrack and field? How long do you like to run in track and field?

I honestly have no idea.