No problem at all! sewers all in your boat once, not so long ago. Ask anything. I will do my best.
Yes you need to begin at the beginning each time. You will zoom through the bits you are good at, the games are intuitive, they adjust to your level continually. The best idea for beginning is to set a time limit. Say 5 or 10 minutes. Once the clock in the bottom corner hits your time limit, record your score. That way it will be easy to see your improvement. As you can compare yesterday's 10 minutes with today's 10 minutes. Wor knowing is that the game time keeper doesn't record a real 10 minutes but records 10 minutes of actuall playing time. Good to know if you only have 10 minutes before rushing of to work!
You will know when you need to increase your time to 15 or 20 minutes as you will be getting maximum points repeatedly by then