The Malus is in the very low end of bikes. Your upgrade choices are limited, due to the freewheel threaded hub.
https://www.sheldonbrown.com/free-k7.html
To get up to 10 rear gears you can be into some money, but it's still on a weak/cheap hub. Using a different range 7 gear or using 7 within 8 gears is common. Upgrading the hub can be done ($) so you can use cassettes, but you need one to fit the spoke count.
A triple mountain front is also used, manually switched depending on the terrain you're on (i.e., flat getting to a trail vs. out on the trail).

The Malus and Dolo are very similar.
You have a lot of reading to do.
The start of the thread is as we figure things out, but it has some common/popular upgrades listed. The middle has more experience gained. Towards the end of the thread, there's a mix of greater experience, newbies and some lost souls.
https://forums.mtbr.com/fat-bikes/dolo-semi-wild-mongoose-dolomite-902410.html

 

thank you canoe .... I read the thread and just sold the malus and buying a better brand fat tire bike .... im 63 and 300lbs and love the feel of the fat tire bike!!

im looking at a DD or a specialized ..... the DD looks better tom me?

your opinion?

 

I'm glad you gave up on trying to make the Malus do something it's not made to do. Particularly the hubs...

I don't have experience with either of those bikes, but others that do have posted here in many threads. Search. A few threads have directly addressed the need to handle higher weight riders (Clydes / Clydesdales), upgrades, riding posture, handle bars & grips, etc., to make riding comfortable so search for those too.

If you don't have the need for floating on sand, snow, etc., consider 27.5+ 4" and 29+ 3" as an alternate for 26 Fat. They came available after 26 Fat and a lot of fat riders have picked up one of the others for three-season (or year round) use (assuming Fat was for snow) and most report really enjoying it. With your weight, I'd expect either to have a better steering experience over 26 Fat, which has higher sidewalls and can result in some "self-steer". There are threads here comparing 'formats'.

Good luck!

 

Once you find those threads, ask specific questions there. Don't forget to provide the type of riding you expect to do and on what type of terrain.