I think most people have problems with the Internet because we spend many hours using it.

It's very difficult don't usto not use the Internet because you use it in yourat work, when you study or in your spare time, f. For example, you use it to watch videos, play games or seewatch movies.

In fact, we use the Internet ion our mobile phones, and we weartake them to everywhere.

In America, it is more common to say "cell phones" instead of "mobile phones", but both make sense.

We use our mobile phones not only to make calls but also to reading the news, usinge WhatsApp and other social networks, etc.

In American English, we would say "cell phones" or "mobile phones", but never just "mobiles". I'm not sure about British English here.

To sum up, we use the Internet constantly and practically for everything, so, i. In my opinion, we are addicted to this technology, and most of the time we don’t realise of this worrying fact.

"Realise" is the British spelling. "Realize" is the American spelling.

I only broke it up into two sentences because it was a run-on sentence. When writing, if you use more than one conjunction (like "and", "so", "or") in a sentence, that usually means it needs to be split up. When speaking, it does not matter as much.

I think most people have problems with Internet usage because we spend many hours using it.

'problems with internet' could also mean technical problems so this makes things clearer, your sentence was technically correct though.

It's very difficult don't usto not use the Internet because you use it infor your work, when you study, or in your spare time, for example to watch videos, play games or seewatch movies.

In fact, we use Internet ion our mobile phones and we weartake them to everywhere.

We use our mobiles not only to make calls but to reading the news, usinge WhatsApp and social networks, etc.

To sum up we use Internet constantly and practically for everything, so, in my opinion, we are addicted to this technology and most of the time we don’t realise of this worrying fact.