Thank you for your question about the difference between repeat and restate.
In a sense, repeat and restate are similar in that they can both mean that someone says something again. However, if someone repeats something, they say exactly the same words, whereas if someone restates something, they express the same idea but by using different words. They do this in order to make their meaning clearer or to make their point more strongly. This is the kind of thing that a university lecturer might do to explain a complicated theory or that a politician might do when clarifying a new policy.
In the following example the second sentence is a restatement of the first sentence.
The government will reduce income tax next year. We will take less of the money that you earn.
Whilst in the following version, the second sentence is a repetition of the first one.
The government will reduce income tax next year. We will reduce income tax next year.
There is, of course, another difference between repeat and restate. You can repeat an action, you can do something for a second or a third time, but it is impossible to restate an action.
So, if you are still not sure about the difference I suggest you read or listen to this explanation again, as it is often said that repetition is an important part of learning.