a lot of storage space is used by "other" . how to remove ?

The Other category is a potpourri of files. They can be located anywhere on your hard drive. The files that you have control over are located in the Documents, Downloads, Pictures, Music and Movies folders.  You can use either of these two free apps, GrandPerspective  or OmniDiscSweeper, 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.  Many users have found a couple of Gigabytes of files in their Downloads folder which are no longer needed. 

I actually did found the largest files on my mac and deleted them. Whatever I have deleted so far is getting accumulated in the other folder even after emptying the trash.

I think there is some other problem, but I cannot get it figured out. Where else I can seek help?

I've used them both. All they do is scan the hard drive and present the files and their size in a graphical format and tell you where they are located. Then it's up to you to go there and copy them to another volume or delete them as the case may be.

The Other category is a potpourri of files which can include:

• System temporary files

• macOS system folders

• Archives and disk images (.zip, .iso, etc. - often found in the Downloads folder)

• Personal user data

• Files from the user’s library (Application Support, iCloud files, screensavers, etc.)

• Cache files: browser, Mail

• Mail messages & attachments

• Fonts, plugins, extensions

• Safari reading list

• iTunes backups

• Crud resulting from jailbreaking your iDevice

• Game data

• Saved data files

• Call history

• Notes

• Media

• Voice memos

• Other files that are not recognized by a Spotlight search

• Media files that cannot be classified by Spotlight as a media file because they are located inside of a package

They can be located anywhere on your hard drive. The files that you have control over are located in the Documents, Downloads, Pictures, Music and Movies folders. 

Don't forget you can empty the Downloads folder after you've install whatever was downloaded to that folder.

Very Good article on this very topic over Here

Has the article provided earlier or either of the two Apps @ Old Toad suggested been attempted ?