Can independent applications cause roll back to each other's transactions?

I have a database built on SQL Server **Application-1 [Legacy App]:** Written in C#, and runs transactions on the above database. **Application-2 [New application being developed]:** Written in Python, and runs transactions on the above database. **Considerations:** - These apps access the same set of tables and perform similar actions. - We are trying to transition from older app to the newer one over time. - I am finding several deadlocks and rollbacks happening in the system. **Questions** 1. I want to understand if there is a possibility that transaction being run via one application can affect the ones from an independent other application. 2. Are these scenarios handled by the DBMS itself internally or have to be handled at the application level ?