so i have a macbook air early 2014 with big sur and 4gigs of ram its a bit sluggish and i wanna downgrade to the stock os that would ha v e shipped with the macbook but idk how to do it im new to macs anyone got a step by step guide for this
Be sure to back up any important files first - to downgrade you should do a 'clean' install by erasing the disk.
None of these older versions receive security updates any more, including Big Sur, and you'll probably run into problems related to expired certificates if you go very far back. I personally would try Mojave and use an ESR version of Firefox for web browsing. The Early Intel Macs forum may offer more advice.
The very first thing you should do is back up your data. If you don't want to read and follow the information in the links I provided above, you could download and use the Mist app from github and use it to create a Mojave installation USB. You'll find the download link on the right, under Releases. You'll need a USB stick or disk at least 16 GB big.
Doing a clean install involves completely erasing the disk, hence my repeated advice to back your data up. That's also why I suggest using an installer USB rather than running the installation app directly from Big Sur - if things go wrong, you can try again.
There are many articles on the web, like this one, which explain the process better than I can. If this is your only computer and you can't afford to be without it, then maybe you can find someone with experience locally to help.