Why on English sometimes the same pronoun are use repeatedly in the same sentence?
It's formal or informal?
For example:
"I" have a dog and "I" love it.

Question

Answer

It's neither formal nor informal - it's simply correct, neutral English.

In some languages, such as Spanish, you can omit pronouns more often than in English. In English, you can rarely miss out personal pronouns.

Answer

Usually english verbs do not indicate the actor, so a pronoun is needed.