Unfortunately, you are obligated under the lease whether or not your business is successful. As for the money you put into the rental premises...look to the terms of the lease to see whether any improvements you make are done at your own risk. I highly doubt that your landlord is going to pay you back for any improvements you made to the premises.
If you don't pay the rent, your landlord can evict you. Depending on the terms of your lease and your state laws, your landlord may be able to accelerate the entire amount of rent due and owing under the lease and take legal action against you for the outstanding amount. If you signed a personal guaranty (which is common in commercial leases), your landlord might come after you personally.
Frankly, if I were you I'd consult a bankruptcy attorney. I'm not saying that you should file bankruptcy, but there may be ways to alleviate the debt owed by your restaurant. There may also be other protections available to you.
DISCLAIMER: Brandy A. Peeples is licensed to practice law in the State of Maryland. This answer is being provided for informational purposes only and the laws of your jurisdiction may differ. This answer based on general legal principles and is not intended for the purpose of providing specific legal advice or opinions. Under no circumstances does this answer constitute the establishment of an attorney-client relationship. For legal advice relating to your specific situation, I strongly urge you to consult with an attorney in your area. NO COMMUNICATIONS WITH ME ARE TO BE CONSTRUED AS ARISING FROM AN ATTORNEY-CLIENT RELATIONSHIP AND NO ATTORNEY-CLIENT RELATIONSHIP WILL BE ESTABLISHED WITH ME UNLESS I HAVE EXPRESSLY AGREED TO UNDERTAKE YOUR REPRESENTATION, WHICH INCLUDES THE EXECUTION OF A WRITTEN AGREEMENT OF RETAINER.
I'd like to know if the lease you signed obligates you personally, or if you protected yourself by using a corporation or a limited liability company. If you protected yourself on the front end then the landlord's remedies for your non-payment are likely going to be limited to something called rent by distress, where they can try to take your property located inside the premises. That would be done by the appropriate Magistrate Court.
If you signed personally, or made a personal guarantee, then the landlord might try to obtain a personal judgment against you for the remaining payments. I think the first step for you would be to carefully review the lease to determine exactly what your exposure is, and then consider whether or not you need to take any additional steps.
Depending on your situation a lawyer might be able to help negiate something with the landlord to give you credit for your improvements if you were to voluntarily give up possession and leave them intact.