How can I optimize the use of my mobile Internet?

I have a dual SIM card, and my Samsung phone is 4G. I don't know anything about the Internet or computer science, but I just want to know how I can optimize my mobile data usage. SIM 1 has used up around 40 GB of data and is really fast. SIM 2 has used up around 40 MB of data and is really slow. I don't understand why SIM 2 is really slow even though I've obviously used up less data than from SIM 1. At the end of the day, I'm paying for both plans, so how can I optimize my mobile data usage?

2021-04-05T18:04:31Z

the speed is the speed of the tower it connects to.
get a better SIM.
however, i don't think you understand what dual SIM is supposed to be used for...
https://en.m.wikipedia.org/wiki/Dual_SIM