Please help: price negociation after home inspection?

XDJM, sorry I can't type Chinese here...

It is a very very helpful forum here, and I have learned so much about home. Envy those with beatiful homes!

I am buying a house right now and have so many questions. Hope someone can come to rescue!!

Here is one problem. We have made an offer ($2000 less than the listing price) to this house that we are interested, and the seller has signed the contract. We have 7 days to complete the home inspection. However, we found out later that the seller answer "unknown" to the question about any previous repair of the foundation in the SDN. The home inspection should check this, right? If we find out any problem about this or other problems, such as that roof needs repair etc., are we still able to negociate the selling price?

Any suggestions will be appreciated. Thanks a bunch!!