I assume English-speakers would understand your intention, but I think it's better to say:

• Can I borrow your phone?

You can include time length and reason for clarity:

• Can I borrow your phone for half an hour? Mine is out of power and I need to lookup something on the internet.

"a bit" and "a little bit" are primarily mostly used for quantity rather than timespan. "a little" is commonly used for size.

I assume English-speakers would understand your intention, but I think it's better to say:

• Can I borrow your phone?

Or even better:

• May I borrow your phone?

"Borrow" holds in it the idea of obtaining something for a while.

You can include time length and reason for clarity:

• May I borrow your phone for half an hour? Mine is out of power and I need to look up something on the internet.

"a bit" and "a little bit" are primarily mostly used for quantity rather than timespan. "a little" is commonly used for size, but can be used for timespan too.

• You are a bit (a little, a little bit) late.
• Can I play a little?
• You will have to wait a little (a little bit, a bit) longer.