Hondu, where do you get your information from? I'm sorry but it's clear you don't have any clue what you are talking about here when you actually suggest someone mess around with desoldering a microphone from a circuitboard then disclaim "I haven't tried it but it would work" -- no!!! DO NOT try this, it is a terrible idea for far too many reasons.
Also, Hondu, how do you know it is a hardware limitation? Has GitUp weighed in on the issue as of yet? I am sorry but if you don't know electronincs 101 and are actually recommending people tear apart their devices and screw around in such a nonchalant manner then I can't believe you when you broadly conclude it is a hardware limitation. I've soldered numerous boards but would never even consider this as something I would tackle. it's unheard of.
Before anything else, try tape. Yes, just tape over that hole in the camera body where the internal mic picks up sound. It will muffle the noise significantly, and may even solve the problem. Cheap and easy!
It is also clear you haven't seriously looked at different products when you actually suggest that a good replacement is a GoPro. You clearly don't know what you're talking about when you say they are a good brand here. GoPro is nothing more than a brand name with no substance these days (seriously, search around these forums -- the only time they see positive light is when you say "mount" or "style" alongside it). They have been for a while. Nighttime use is and always has been abysmal (a strong point for GitUp) with insane levels of noise involved, and image comparison tests just do not work well in GoPro's favor even during the day when color is an issue.
Do us a favor: before acting like GoPro is king of the world, check out the actual ranking for this site: the home page dashcamtalk.com , and look at a few others. You will notice GoPro isn't even there and there is a damn good reason for that. Far better cams exist for far cheaper. GitUp is one such brand that continues to not disappoint, but there are other brands too.
And for the record, my GitUp Git1 blows my GoPros out of the water on comparison videos any day of the week, especially when points of light are introduced (LED's etc.), and doubly so at night (or, perhaps more practically for car vlogs, tunnels and bridges). I have two that I still use for YouTube videos myself and despite being discontinued due to newer technology, GoPro has yet to make hardware that comes close. That says a lot about how abysmal GoPros really are that a camera made what, three years ago I think? Still outperforms current offerings.
Bottom line is this: please, unless you actually know what you're talking about, don't just spout nonsense. It's not helpful and at worse, someone may just tear apart their apart their camera under bad advice to try and solve a problem, destroy it, and be left with an expensive brick, and then buy a device that doesn't even meet their needs. We are all here to learn and share but that right there is just levels of dangerously bad suggestions I haven't seen on this forum to date, and utmost caution needs to be urged. Don't tear apart devices guys, unless it's clear that's an okay thing to do (Mobius cams case in point). Ask the manufacturer first, and don't believe everything you read on the internet blindly.
Now, addressing the root of the problem DineshKumarDora is facing, in lieu of a firmware solution, try electrical tape (layer them up if need be) over the hole for the internal mic, combined with one of those "underwater" style GoPro mounts. The cheap clear plastic ones that are watertight. Essentially, the point is to literally muffle the internal mic while also protecting the cam from dirt, grime, etc. If done right, the noise should be so inaudible that it can be ignorable. If all else fails, a recording device isn't a bad thought (Android has a few apps for recording audio for example -- by the way, disable WiFi for car trips so it doesn't interfere with the cam), then video editing can sync it up. OpenShot is fairly full-featured and free software for video editing if you need it, there's one with AVI in its name people use too for more basic tasks, but I like the boatload of extra features OpenShot provides.