Apps taking a lot of space in disk

The files that you have control over are located in the Documents, Downloads, Pictures, Music and Movies folders.  Also the Applicaations folder if you have any that you'd like to delete to regain some space. If you do delete some apps be sure to also delete their support files. Those are easily identified and delete with the free app AppCleaner 

WARNING: If you use AppCleaner on an app that you have other apps from the same developer, like Adobe, you must be extremely careful checking all checkboxes and deleting.  Some for those files may support other apps from the same developer and deleting them can mess them up.  Adobe apps is a primary example. I know from experience.  For singular apps from a developer it's safe.

You can use this free app, GrandPerspective, to find the largest files on your drive so you can determine if they can be deleted or moved to an external HD for storage.

Note: you can empty the Downloads folder after the apps and/or updates that were downloaded have been installed or applied.  Some users have found a couple of Gigabytes of files in their Downloads folder which are no longer needed. 

Mostly i am using the Adobe Photoshop and Lightroom for editing images.

Does something have to do with those apps?

Yes, most image files are large. If you store lots of them on your Mac storage, that will show up under Application storage size because the files are associated with the app.

Do you have any apps that produce large files like graphics or movies? That storage display is not just the size of the Applications, it also includes the data created by the app.