Great question — answering as the UphillTech team:
"shimano tourney" suggests your bike is definitely entry level, so dropping a lot of cash on it may not be a good use of your money. As an alternative, if you simply want fewer gears, try riding around in one specific front chainring and don't shift the front. It is possible you might be perfectly OK to ride in the big chainring, or perhaps the middle one. It is unlikely you'll choose the smallest/grannie chainring, it is too low for most riding. If you can live in one chainring, then unbolt the other chainrings and store them. If your chainring is rivetted together, then this will be destructive and going backward is impossible. You remove the front shifter and wire, and it is possible to...
Full answer by Criggie: https://bicycles.stackexchange.com/a/79557 (CC BY-SA 4.0).
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