I cook.
My mother cooks
She cooks.
He cooks.
My father cooks/roast.

{My father} is the third person singular, so please add an s at the end of {toast}.

My father cooks/roasts.

I fry the fish.

I fry a fish.

We fry two eggs.
He fries two fishs.

When {fish} is used as a countable noun, referring to the number of fish, the singular and plural forms are the same, while when referring to the species of fish, the plural form is {fishes}.

He fries two fish/fishes.

Baby sucks his thumb.
His mother soaks the beans.
She squeezes an orange.

She cooks nice.
My father cooks fast.
She digests slow.
He bakes delicious.
Nina roasts tasty.

We use adv. instead of using adj. here.

She cooks well.
My father cooks fast.
She digests slowly.
He bakes well.
Nina roasts well.

pepper is spicy.

The first letter of a sentence should be capitalized.

Pepper is spicy.

I am student.

We should add an article {a/an/the} before a singular countable noun.
For example, we should write {a student} here.

I am a student.

you are girl.

The first letter of a sentence should be capitalized.
We should add an article {a/an/the} before a singular countable noun.
For example, we should write {a girl} here.

You are a girl.

she was teacher.

The same reasons mentioned above.

She was a teacher.

There were party.

{Party} is a singular countable noun. We use {was} instead of {were}.

There was a party.

Apple will be sour.

We should add an article {a/an/the} before a singular countable noun.

The apple will be sour.

subject+verb+to+verb

Alice walk to dance.

{Alice} is the third person singular, so please add an s at the end of {walk}.

Alice walks to dance.

She need to run.

{She} is the third person singular, so please add an s at the end of {need}.

She needs to run.

He want to jump.

{He} is the third person singular, so please add an s at the end of {wants}.

He wants to jump.

subject+verb+noun+to+verb
She carries a beef to toast.
He busies the pepper to cook.
I choose a book to read.
Nina compares the tool to use.
Nomi jumps on table to eat.

I believe you want to say {buy} here. And its third person singular form is to add an {s}.
If a verb ending with {a consonant letter + y}, we will change {y} to {i} and add {es}.

He buys the pepper to cook.

She cooks nicely.
My father cooks fastly.
She digests slowly.
He bakes deliciously.
Nina roasts tastily.

{Fast} can be an adj. or an adv. We never use {fastly} which is a wrong word.

My father cooks fast.

We usually use {well} to indicate that a person has excellent cooking skills

She cooks well. He bakes well. Nina roasts well.

This pepper looks spicy.
I taste bitter.
The girl seems sad.
She becomes a teacher. (noun)
The music sounds great.
The apple looks sweet.

{Bitter} is an adj. for sth.
You can say {sth. is/tastes bitter}.

It tastes bitter.