About sqlcipher DB size limitations

SQLCipher
2

It is about 1.4 Mb size this database after much use of it and the
encryption doesnt work. It doesnt encrypt the data allready exists in
that database

See How to encrypt a plaintext SQLite database to use SQLCipher (and avoid “file is encrypted or is not a database” errors)

SQLCipher should report an error if you attempt to use sqlite3_key or
PRAGMA key on an encrypted database. Did you not see the error? Is it not
clear enough?

I think 1.4 MB is not a very big SQLite database. Web data storage is at
least 2MB for LocalStorage, at least 5MB for Web SQL or IndexedDB as
described at web.dev.
SQLite limits described at Implementation Limits For SQLite are much
higher (over 100 TB).

Will the encryption have problems after long time use of database that
will become bigger and bigger in size after years inside an application ?
(will it encrypt and decrypt without problems?)

My understanding is that SQLCipher should be able to handle many gigabytes
and even multiple terabytes by design. I leave it up to the SQLCipher team
to provide some further details.