Question about iPhone?

I have an iPhone 6, while my crush has a larger and more updated iPhone.
They sent me a cute video of themself over text, so I downloaded it onto my pictures and I can't watching it, they're sooo cute.
Can they tell that I've downloaded it and/or kept watching it over and over again?

I don't think so

If you're using the Messages app then no, it doesn't tell the sender that you downloaded their pictures and videos or how many times you've looked at it

No. Assuming by "text" you meant iMessage (which isn't text messaging for the record) the very least they could do is know you've received the message & seen the message. If it contains content, they can't tell if you downloaded it or did anything with it after it was downloaded.

Though it was a little confusing cause you said you "can't watch(ing) it" but then said "kept watching it over & over again"