Just imagine you're a high-jumper and you're practicing the high jump now. If we set the bar at a very low height, let's say 3 feet, you would jump over the bar without any doubt. in this situation we say 你过来了。 Okay, now let's raise the bar to 7 feet, I am sure you wouldn't be able to jump over the bar, in this situation we say 你不会跳过来 or 你不会过来。 So back to your sentences, normally we use 不...过来 when we can't cope with something or can't handle a difficult situation. It is kind of a figurative use of language. 这里事儿太多，你一个人忙得过来吗？There're too many things to deal with, Can you manage them all yourself? 这里事儿不多，我一个人能忙过来。There're not many things to deal with, I can handle them all by myself. Send me message if you still dont get it. :-）

De is a very special word in Chinese ,as you cant find this in anyother languages perhaps. Its function is to express a result or degree ,very much similar to "to which degree" any verb followed with buguolai means can't handle with. Almost all means quite the same emphasing the concept of being too busy to do sth

this structure is .......忙得過來 can handle sth , have enough time to finished it .........忙不過來 cant handle sth, dont have enough time to finished it.

thanks so much dear!

得can use as a adv. verb +adv.+sth,haha ,你中文真的不错