Great work, but a bit ambiguous at the end
I thought you did a great job of telling the story without any dialogue. If you can do it effectively (and it seems you can) then I don't think there's anything wrong with leaving voices out of the picture. The music was well-chosen, although the volume of 2nd track towards the end was noticeably low.
I thought your animation was good, although some of the minor characters (like the robots) seemed more detailed than the main character. The minimalism in detail worked well with the girlfriend, but I thought the protagonist could have used a bit of spice. Also, I think a fight scene between the couple might have helped illustrate the strain on their relationship a little better -- the montage showed me he was working on a time machine, but it wasn't as clear that he was placing excesssive strain on his relationship.
Finally, I didn't quite understand where the protagonist was going at the end.
SPOILER ALERT
I gathered he was going back to remedy the situation with his girlfriend, but didn't know precisely when he had in mind, and thought it was a mistake to leave that out. It felt like you cut things off at the third act, or maybe at the climactic moment, depending on what you envision the protagonist doing. It may also have worked better if he had been spiteful and actually gone to the future (maybe set up a bank account in the present and got rich?) before realizing that love was more important.
I can see how using the time machine to fix things might be problematic -- is he going to convince himself not to make the machine and hope it changes his own timeline, or what? If it seems like the circumstances in which he could fix things are too complicated or unlikely, it might be better to end it on a sad note -- let him get the most out of his time machine, but end it with him sadly observing his past self and the love he lost. I don't know what you'll decide to do, but I do hope you do something. You have the makings of a great story here, but I think you need to revisit it and consider its plot and theme. It's good in its current form, but feels unfinished.