Deleted app, new install: chats, contacts... how to get them back?

Valued Delta-chat team, developers, user,

(pardon if it has been already a FAQ here already)

Delta Chat version

1.14.4 android

Expected behavior

Having delete the app and then installed again, it was expected to find all chats and contacts again (datas).

Actual behavior

Empty of all datas, at least not displayed.

Steps to reproduce the problem

What can be done, if something can be done, to get ones old datas back?

If a new installation requires certain backup first, how to progress in easy way?

Not sure if this was related (or had worked either “alone” as being just a matter of some time), but after having followed a “workaround”, seen in another topic, by copy all messages is a temp folder and then back into delta folder on server, most seems to have reappeared. Just certain chat-logos didn’t and of what and where contacts are stored and can be maintained, this is also still a stranger. “Gained contacts” while having used delta, after new installation, seems to be gone when there is no communication, mail, left with the contact. To get most contacts back it’s required to go through the “contact requests” manually and adept to have a chat first, at least open this dialog.

(My person trusts that repeated “musing” and public reflexions here by him are of use for others and not general useless considered)