Oracle database not open and ORA-00600 error
It looks like your database experienced an incomplete recovery. This is why it complains about open resetlogs. After an incomplete recovery you need resetlogs. To be able to get this database up and running again, you need to know what caused the current situation and some skills to get it out of there.

If the data is not important at all, just trash the database and create a new one. The actions needed for this depend a little on the platform where you are on.

the documentation looks like a good starting point.