I went to a/the community pool

Yesterday I went to a/the community pool with my friends.
I didn't have swimming wear (<em>Or:</em> swim clothes) for the pool.
At first we went to a sports shop and bought it some.

It was raining. We felt the water in the pool and shower (to be) cold.
My friends usually go to the pool in the sports gym.
The pool in the gym is (<em>Or:</em> has) controlled water temperature, so/and it is warm.
So he was specially felt cold. So it <em>(the community pool?)</em> felt especially cold.

I gave up to swim swimming after only 150 meters.
My physical strength considerably declines.
I want to train to acquire (more) physical strength.

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Good job! You did well with basic English sentence structure.

Before a singular count noun, such as "community pool" or just "pool", you will need to use a determiner 99% of the time. Determiners include articles (definite/indefinite/zero), demonstrative pronouns (this/that/these/those), and possessive pronouns (my/your/his/her/our/their). You used "the" in the line "<em>The pool</em> in the gym..." This is correct. But you also have to use a determiner before each other instance of "pool," as well as before "shop," which is also a count noun. You also wrote "the gym" twice, which is correct: since "gym" is a singular count noun, you will almost always use a determiner before it.

2. Use 'it" if you are referring back to the community pool!