1. Your English is spot on
2. Make sure to use a custom character. You should use your main character (the character you play as the most) too. Select the custom specials you prefer, then move on to equipment.
3. With equipment, you really want a lot of defense. However, this doesn't just mean put a lot of defensive equipment on. Choose things like KO Heal or Auto Heal or First Striker Bonus. Also, I find that holding a beam sword in battle is great, as you can constantly do your side-smash attack with the sword from a safe distance, therefore take less damage. Some of these pieces of equipment you will not have, but just try to pick the things which will benefit you the most in battle.
4. Remember, 9.0 is HARD! When choosing your opponents, think about how you would go in that battle. If you see a battle where you will only verse 1 opponent, that will be an easier battle than a battle against 7 opponents. Even if you see an opportunity to get something rare like a crazy orders pass, unless you feel confident in surviving the battle, think twice before rushing in.
5. If you make it to Stage 7 (Mater Core battle), this is the hardest part. Remember Master Core's different stages, and make sure you know the types of attacks they use. Going into the fight for the first time, you will probably lose easily. To get used to his attacks, you should practice on 8.0 or 7.0+. Also for this final part, if you use someone who can counter (Marth, Lucina, Roy, Palutena, Shulk, Ike etc), you can counter some of their attacks, and do BIG damage. This is where knowing his attacks is really important.
6. Don't be disappointed. If you don't beat it the first, second, or even tenth time, don't be disappointed. I can't even beat him on 8.0 (although I've been close, I have never entered Master Fortress). It may be that 9.0 just is too difficult for you, and that's ok. I know 9.0 is too difficult for me.
I hope this helps you beat 9.0 Classic, and sorry for the very late response.