Is it a good idea to add a shortcut to a gallery from the modal I am in, instead of closing it to go back to the gallery?

In my app I can access a gallery (1) and, after selecting one of the items, I can perform an exercise ( 2- MODAL). It is a training app and in the modal I am going to choose what I think is the correct answer to the previously chosen item, which is merely a preview of the exercise itself shown in the modal.

When I am in the modal, I was wondering if I can facilitate navigation by allowing the user, in addition to the 'next' in the upper right corner that would bring to item 11, to select a specific item/exercise by adding a collapsible section (3) by tapping the arrow indicator next to '10' in the nav bar. I could access the same gallery as screen (1) and choose a specific item from there instead of clicking next an stick to the order I am given of closing down the modal to choose something more specific.

Is this any good or am I just messing things up?

More context and additional info here. The total number of exercises are about 50. These exercises are logic stuff, provided by an institution. It doesn't matter if I already performed them, they're part of a training and may be randomly picked up when the user takes the final exam. The goal here is to solve them over and over or insist on specific ones if I don't remember the logic behind and need to refresh things up. The preview in the gallery is a preview of the exercise itself, so with a glance I can select what I need. When you click verify, you may want to re-tap it to see the solution once again (it may be called play instead of verify).You choose what to do next then, if closing down the modal after just one exercise, pick up a specific one by tapping on the arrow indicator, or simply tap 'next'. Completion in a sequence is NOT a requirement they can skip exercises and nothing would happen. Is the arrow indicator a good thing? Or it adds nothing?