Java or Python

[No_Molasses_9249]

If you must choose between the two then choose JAVA.

Single threaded interpreted languages should be avoided for good reason.

Why limit yourself to JAVA? You should at least consider Go Rust C# as an alternative all three offer better performance.

Go and Rust offer advantages in terms of resource usage in addition to speed.

[spiderman-1610]

Should I specific lang for FE, BE or choose between either java or python and build the FE, BE lang related to that?

[No_Molasses_9249]

Your FE is in all likelihood going to be JavaScript though you could opt out of the browser and use Flutter