Actually there are so many ways to try out...
but i just list out 4...
*macam la korang nak try...huhu
anywayz...just sharing this info....;)
1. Uninstall any extensions or themes you do not use. Go to Tools > Add-ons, simply select any extension or theme you do not need, then click "Uninstall".
2. Uninstall any plugins you do not need and download the most recent versions of plugins you do use. To see your installed plugins, open a new tab or browser and type in the address bar "about:plugins". Hit enter. To uninstall any plugins, you will typically need to remove the file associated with that plugin. The file name will be listed under the plugin name.
3. One of the best ways to speed up Firefox is to clear out your private data. In your browser, click Tools > Clear Private Data. Check everything, unless there's specific data you'd like to save. Click "Clear Private Data Now". Note that your private data includes browsing history, your download history, your saved forms & search history, your cache, cookies, offline website data, saved password and authenticated sessions. Firefox gives you the ability to pick and choose which data you'd like to erase, so you do not have to delete everything in your private data. Keep in mind however, the more data you keep saved, the less faster Firefox will run.
4. For continued maintenance, select for Firefox to clear out your private data every time you log off the browser. Go to Tools > Options and check the box under 'Private Data' that reads "Always clear my private data when I close Firefox". You can change what data Firefox clears by selecting the Settings option and checking or unchecking the boxes.
credit to
snowbite