How to use two different numbers in the same phone via WhatsApp? My phone just went broken last night, and I have another but I don't want to change the SIM card, so I'm wondering if it's possible to run 2 numbers on the same phone.
I have heard there is a chance of creating a new user and installing WhatsApp again under that new user, will this work? I don't want to lose a couple of work groups that are important.
There are multiple possibilities:

Some stock/custom ROMs (e.g. MIUI) let you create a new user with a non-zero ID by utilizing the Multiple Users / Work Profile feature of Android. You can switch between accounts and almost all installed user apps can be duplicated with unique settings/data for each user.
You can use some dual account app; a kind of OS-level virtualization or containerization. There are numerous on Play Store like Parallel Space. But personally, I don't recommend this option as these apps are a burden on resources and may slow down the device or reduce battery timing. Most of those require too many permissions, seem focused on ads, user stats, analytics, and tracking for monetizing. Shelter is an open-source (FOSS) app if you go for this option.
Another option is to use a modded WhatsApp with a different package name e.g. GBWhatsApp. That will work in parallel with the official WhatsApp release. Be aware of illegality and malware when going for non-official apps.