How to Update Theme?
Please make sure that you did not make any changes in the files. If you have made changes and you do not want to lose them, the best way is to use one of freeware tools for comparing files. After comparing these files you can upload on server only the files that has not been changed.
If you have not changed any theme files, all you need to do is update your version of theme by downloading the latest package from themeforest, unpacking files and uploading new files on the server while replacing the old files. Simply overwrite them.
All your data in the database are safe because after updating theme files does not change anything in the database. Please however always make a backup of your files & database.