There is a simple method that i use and i don't have to donwload everything when i do this.
I'm an android user so it's simple by browsing in you folder files of DBL in your phone.
1 You have to locate you dragon ball legends folder within your phone (usually is in you local memory / Android / data and then you have to find the folder "com.bandainamco.dblegends_ww")
2 You have to rename the entire folder by ADDING a word ( usually i add a "n" in "com" so it's will be litke this "comn.bandainamco.dblegends_ww")
3 Don't worry if you don't see you folder anymore becouse you have to scrool down in the data folder to find it
4 Now delete your install of your original or Mod game and the install the apk Mod or original install from Google Play Store (DO NOT OPEN THE GAME AFTER YOU INSTALL THE APK MOD OR THE GOOGLE PLAY INSTALLATION)
5 Now you have to go in the data folder that i previously metioned and rename the "comn.bandainamco.dblegends_ww" in "com.bandainamco.dblegends_ww" without the quote ( BE CAREFUL TO RENAME THE FOLDER AS I SAID BECOUSE YOU MIGHT HAVE TO DOWNLOAD EVERYTHING IF YOU DO A MISTAKE )
6 Now open the game and give the authorisations that the game ask you to give in order to read you folder and gamedata that you alredy have
7 Enjoy
PS I do this every time DBL update so i don't have to download everything from the scratch
You are free to ask me anything if you don't understand