I own a house in Germany and have the mortgate with a German Bank. Can I claim the property tax and mortgage interest?

[Opus 17]

Yes, subject to the usual rules.  You can deduct qualifying expenses even if paid to a non-US bank or municipality.

Real estate taxes that are deductible must be charged at an equal rate to all homeowners based on property values and pay for general government services.  Items that might be specific to you or your neighborhood are generally not deductible even if they appear on your tax bill.  For example, an extra charge for the homeowners on your street that pays for sidewalk maintenance is a specific benefit to your property and is not deductible.  See here for more.

https://www.irs.gov/publications/p530/ar02.html#en_US_2016_publink100011838

Mortgage insurance is deductible for loans used to acquire or improve your main home and one second home.  There are limits on the amount of home equity debt you can finance.