Learn English – the difference between booking and renting something

It depends on a context. They both may mean the same thing in example like this -

He can hardly write = He can barely write

But then, if you check all the meanings for both the words, you may come up with an example where the words cannot be interchanged.

Now, when in case where hardly refers to 'almost never', replacing it with barely may not sound natural.

"I hardly go for a social gathering" over "I barely go for..."

Edit after the question is edited:

Yes, I agree with djechilin (+1), use poorly or badly instead. The book is poorly translated.

The difference is in the degree of change applied to the object.

Enhancing leaves the main structure and functionality the same, most features intact, and generally speaking improves the object by applying small modifications.

Revamping often changes the basis, some fundamentals, some key features. Structure can undergo some changes, but the functionality generally is kept as is although we can see re-prioritizing of some elements.

Overhauling involves disassembling into constituent parts, examining each of them carefully for flaws, replacing with equivalent new parts (subsystems), in order to bring the system's performance closer to the original specification/idea.

Those words are not interchangeable. You could overhaul an engine of an aircraft to bring the engine back to its "factory new" performance. You could enhance an engine of an aircraft by replacing some heavier parts with lighter ones, for instance. You wouldn't revamp an engine. The latter most often used to describe a process for making fixes in a social/business system, like government, company management, etc. You could, however, revamp a design of an engine, which often includes technological part (manufacturing).