Overall the English is pretty good, but it sounds just a little unnatural so I'd make the following changes:
"We understand your concerns about your laptop not closing properly, and we would be more than happy to help."
By saying "we are very concerned" you make it seem like you are panicking or more worried than you actually are which in turn might make the first person more worried thinking things like "Oh no, does this mean my laptop will not be able to be fixed?"
"your comments on your laptop not closing properly" sounds a little strange. Even though it's technically not wrong, people wouldn't say this. This is kind of hard to explain, but its just phrasing more than anything I suppose.
"when placing the cloth over the keyboard" can be omitted. You do not need to restate the issue here because it's already understood between you and the person your speaking to and adding it in this sentence makes it start to sound like a run-on.
"we would love to help you out" is just as good as "we would be more than happy to help." Both are good here, but the second is a very common replacement and I'd argue more used, so it might make you sound more natural.
Hope that helps!