Hello Sylber,
If both application share the same local entities then, when installing over the existing application, no data should be lost.
If the local entities are not the same you can, for example, have a synchronisation where you move the data from the old tables to the new ones. After every user has done this you can stop consuming the old tables.
Please check which option suits you better.
Best regards,
Gonçalo Condeça.