Hi there and welcome aboard @Andres4 
Our Google Reviews widget has a restriction on displaying only 100 last reviews, that’s why older reviews are not displayed in your widget.
We agree that it would be awesome to display all reviews and we have such a request in the Wishlist. You can vote for this idea in this thread - Display all reviews in the widget (remove 100 reviews limit)
Please let me know if this clarifies the situation or if any further questions come up 