no such table SQLITE

[dplusk]

Hi, I'm a noob in programming android apps. When using SQLite Database I got following problem:
Logcat tells me: "no such table: table1", when I run both methods. Where is my mistake?
I use an existing database, placed in assets/databases folder.
MainActivity

package com.dplusk.example_sql;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    DataBaseHelper dataBaseHelper;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void onClickSearch(View view) {

        dataBaseHelper = new DataBaseHelper(MainActivity.this);
        try {
            String post = dataBaseHelper.getPost("table1","Moser");
            Toast.makeText(this,String.format("%s",post),Toast.LENGTH_SHORT).show();
        }catch (Exception e){
            Toast.makeText(this,"Error",Toast.LENGTH_SHORT).show();
        }
    }

    public void onClickUpdate(View view) {
        //Toast.makeText(MainActivity.this,"Saving successful",Toast.LENGTH_LONG).show();
    }

    public void onClickRows(View view) {
        dataBaseHelper = new DataBaseHelper(MainActivity.this);
        try {
            long count = dataBaseHelper.numberOfRows("table1");
            String message = String.format("%s",count);
            Toast.makeText(MainActivity.this,message,Toast.LENGTH_LONG).show();
        }catch (Exception e){
            Toast.makeText(this,"Error",Toast.LENGTH_SHORT).show();
        }
    }
}

DataBaseHelper

package com.dplusk.example_sql;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import androidx.annotation.Nullable;

public class DataBaseHelper extends SQLiteOpenHelper {

    public DataBaseHelper(@Nullable Context context) {
        super(context, "database.db", null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    }

    public String getPost(String table, String nameIn){
        String queryString = "SELECT post FROM "+ table +" WHERE name = "+nameIn;
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(queryString,null);
        StringBuffer buffer = new StringBuffer();
        while(cursor.moveToNext()){
            String post = cursor.getString(0);
            buffer.append(""+post);
        }
        cursor.close();
        db.close();
        return buffer.toString();
    }

    public long numberOfRows(String table){
        String queryString = "SELECT * FROM " + table;
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(queryString,null);
        long count = cursor.getCount();
        cursor.close();
        db.close();
        return count;
    }
}

Please help me.