To create new affirmative sentences in English, follow these three steps:

1) Say or write a sentence in English:

I drink juice.

2) Repeat the structure, and change one word at a time:

I drink milk. I drink water. I drink coffee.

3) Continue the process, with all the sentences you already know:

I eat bread. I eat cheese. I eat pizza. I eat popcorn.

I like my mother. I like my father. I like my sister. I like my friends.

I speak English. I speak Portuguese. I speak Spanish. I speak Italian.

I know your brother. I know your cousin. I know your teacher. I know your neighbor.

I want to play tennis. I want to sing. I want to dance. I want to run.

Get a notebook and write as many sentences as you can!