"tens of times" isn't really an expression in English. even though it's not a direct translation of the Indonesian word I would say "dozens of times"
The problem is that this lesson also teaches "dozen" so it could be confusing, but I agree
It's funny..."hundreds" or "thousands" or "millions of times" sound fine. But "tens of" just... doesn't.
I agree with the comments above. But I have a problem with the present tense here. I would say, 'i have been to Bali dozens of times'