... I don't understand ... what topic ?
This one:
No ... that is another chat app ... and it works very well ( I made that one to send olny text , not media )
Yes ... but I should delete those options ! 
They are ... fake ! Because they save olny the file position in the smartphone , and not the real file ( like in base64 ) ... So the user that has another phone cannot see correctly that image !
Not intencionally ... that was a my error !
Back to your question.
Personally, I would recommend that you use an online system designed to do what you want to do like Firebase to handle your chat (realtime database or firestore) and storage/delivery (firebase storage) of media files. Firebase can also provide user authentication and rules to handle privacy and security of data and media. In my opinon, cloudDB is not the best solution for what you want to achieve.
Ok , andd thank you ... but Firebase has a limitate storage , so I want to divide the base64 string into small pieces in different tags , and then I want to recompose it .
Can you , please , share to me a schreenshot of how should I use the blocks to make it real ?
If you want to continue to use cloudDB, you should consider setting up your own redis server.
What is a redis server ? I haven't a server !
So ?
I mean that I want a schreenshot of how should I use the blocks to make real the division of the base64 string into small pieces in different tags , that then it will be recomposed in the same blocks .
P.S. :
I want one solution that can make you share images , videos and audios from one phone to another using CloudDB and using this procedure
Split a long string:
Suggest 30,000 characters per split so you will need to do some maths
You would have to create many many tags, for example a 132kb image file generated 19 chunks (@500,000 characters in total).
This is not the way to do things...
I know that you are one of the wisest of this community , so ... what else can I do , if I want that this App will be global , on Google Play ? If it will be on GPlay , I should make one firebase for user manually , that is a bit difficult ...
So , I thought that is simplier to make many tags in clouddb ... but if this is not a good idea , are there alternatives with a theorically endless free storage ?
And I want that the final solution works with images , videos , audios and ... maybe PDF's ( I know that here are some extensions for PDF readers , so I thionk that it will be possible to make the procedure also with this kind ofm files ... )
Thank you for your help . I know that this question is a bit difficult to understand ...
@TIMAI2 , thank you . I'll not "spam" more other topics with my chat app ... even if that wasn't spam
A cost will arise at some point, whatever method or provider you use
And sorry ... I want to help , but I' m making too much mistakes ...
I know that ... I said theorically endless
I'll test something ... for now , this question is SOLVED ! 