Today was a very tireding day. Today was a very tiring day.

Today was a very tireding day. Today was a very tiring day.

Today was a very tireding day. Today was a very tiring day.

Today was a very tireding day. Today was a very tiring day.

I was reading about protein. I was reading about protein.

Or you could also say " I read about protein"

I was reading about protein. I was reading about protein.

I've been reading about protein. I've been reading about protein.

I am reading about protein. I am reading about protein.

Protein is very important for the people. Protein is very important for people.

Protein is very important for the people. Protein is very important for people.

Protein is very important for the people. Protein is very important for people.

Protein is very important for the people. Protein is very important for people.

I prefere thea natural protein, like a eggs. I prefere a natural protein, like eggs.

I prefere the natural protein, like a eggs. I prefer natural protein, like eggs.

I prefere the natural protein, like afrom eggs. I prefer natural protein, like from eggs.

I prefere the natural protein like a eggs. I prefer the natural protein like eggs.

Bodybuildings usingers consume protein in big (large) quantities, but for the rest ofmost people it is not necessary. Bodybuilders consume protein in big (large) quantities, but for most people it is not necessary.

Bodybuildings using protein in big quantities but for the rest of people is noers eat large quantities of protein, but for most people that isn't necessary. Bodybuilders eat large quantities of protein, but for most people that isn't necessary.

Bodybuildingers usinge protein in biglarge quantities, but for the rest of the people, that is not necessary. Bodybuilders use protein in large quantities, but for the rest of the people, that is not necessary.

For things which are general facts, simple present tense works better than the progressive. So, "bodybuilders use protein" instead of "bodybuilders are using protein." "Big" is usually used for physical size (height, width, and volume), but feels awkward when used for numbers and quantities. "Large" might work better here. Here, instead of "the people", I might say "us": "...but for the rest of us..." This might sound more natural.

Bodybuildingers usinge protein in biglarge quantities but for the rest of people ius that's not necessary. Bodybuilders use protein in large quantities but for the rest of us that's not necessary.

We don't use "big" to describe the amount of something, it's used to describe physical size or importance (ie. "a big step forward," "a big moment"). Usually we say "large" but "vast" and "enormous" etc are okay too "unnecessary" can also replace "not necessary"

Bodybuildingers usinge protein in big quantities but for the rest of people is not necessary. Bodybuilders use protein in big quantities but for the rest of people is not necessary.

In the supermarket exist protein products in abundance, its so(grocery store), there are so many protein products it's crazy. In the supermarket (grocery store), there are so many protein products it's crazy.

In the supermarket exist protein products in abundance, its soThere are so many protein products in supermarkets that it's crazy. There are so many protein products in supermarkets that it's crazy.

In the supermarket exist, there's so many protein products in abundance, it's so crazy. In the supermarket, there's so many protein products, it's so crazy.

In the supermarket exists there are protein products in abundance, it's so crazy In the supermarkets there are protein products in abundance, it's so crazy

"there exist" is grammatically correct but sounds very stilted

In the supermarket there exist protein products in abundance, it's so crazy. In the supermarket there exist protein products in abundance, it's so crazy.

It's is a contraction of "it is" in that context it needs an apostrophe.