Hello Mr Matvej27,
Thank you very much for considering my bid on your project. Your requirements seems flexible which is giving me a feeling that you're a developer as well or have been in the past.
A dedicated background service would be integrated with your existing project which makes asynchronous network calls and perform database operations on decision drawn as per your requirement. Since you have need a default database and a downloadable database, we would be required to make separate database file loaded into assets folder.
Please explain your server configurations(FTP/HTTP/etc). You want to check every 5 seconds for database? You are gonna need POLLING approach, the more frequent your network calls the more battery drainage would be experienced. You want the service to run throughout even when the app is closed? Please explain what you want to be done.
I can get all your requirements done in 2-5 days time(depending upon your requirements detail) and keep you in the loop everyday about the process, a brief email or a live chat of 15 minutes would suffice, i believe.
Of course, you won't have to pay a dime until you get all your work done and finished and tested thoroughly. I am looking for a long term business relationships here, so of course we can negotiate on the cost. Please drop me a message so we can begin with it.
Thanks again for your time and all the best with your project.
Regards
mojo43