Property taxes are only deductible if you are the person required to pay them. If the home is in the name of the previous owner, and the previous owner is responsible for the taxes, you can't deduct them even if you pay them.
Mortgage interest is deductible if the contract meets the definition of a mortgage. That means a loan secured by the property, and "perfected" (which usually means it is registered as a lien against the property in the county clerk's office or wherever deeds are recorded. You may need to see an attorney to determine if your contract constitutes a mortgage for tax purposes.
The part of the payment that is not interest is never deductible, that's how you are buying the house. Buying a property or investment is never deductible, and in fact, if you later sell for more than you paid, you usually owe capital gains tax.
Repairs are never deductible, that's the responsibility of any property owner to keep their property in good condition.
Improvements are not deductible, but they count as part of your cost, and may reduce any capital gains when you sell. An improvements is a permanent change to the property that adds value, increases the useful life of the property, or adapts it to a new use. For example, painting is a repair, but replacing carpeting in the whole house will generally be an improvement.
