Factory gearing are use from factory for good reasons and there are plenty other bikes that are more efficient at going faster.
It's hard for me to sustain the tallest factory gearing during my daily commute, simply because traffic pattern doesn't allow higher speed without the danger level going up substantially.
Even with factory gearing, I'm passing cars between mirrors and dodging pedestrians that walks out in front of me without looking.
It's a cheap bike, I keep OEM items unless related to personal fit or comfort.. speed isn't a priority for folding bikes, likely it's not designed to perform at higher speed regularly or safely.