You need studio Pro for this. The documentation on how to work with Eclipse is here: https://docs.mendix.com/refguide/using-eclipse
After that you can see the red dots pointing to errors in the Java code. Did you make any changes in the Java? Otherwise double check your userlib for double jar files. Most of the time that is the sollution. See the screenshot
The saml module uses 1.11, Pushnotifications 1.13 while the Email module uses 1.14. Having all three Jar files would give you such errors. Only keep the highest version and delete the rest. Keep the required files so you know that that Jar is used by different modules.
Regards,
Ronald