Thats not necessarily true. You're thinking about things too simplistically. This isn't Dragonball.
How strong you are doesn't necessarily mean you will win every fight.
Oda makes this clear throughout the story.
Battle is unpredictable. Power Level
does not = Victory. Being strong and winning the fight are two different matters entirely.
These are the principles Oda keeps in mind when writing his fights. Thats why Casear can beat Luffy by catching him off guard with an unexpected ability. Thats why Big Mom can be fended off by the weakest of the Strawhat Pirates. Thats why Luffy can still struggle against Mr 3 back in Little Garden even though we know Luffy is far stronger than him.
It's not always a matter of power levels.