OP, assuming you are playing RS3, chat windows, minimap are resizable, among vast majority of interface components, through Customizations. There are vast degrees of customizations in RS3, and in your case the simplest way to unlock the ability to resize components like chat windows and minimap is by clicking the "lock" icon on the top right corner of your Ribbon.
https://runescape.wiki/images/Ribbon.png?c6ff4
https://runescape.wiki/images/thumb/Interface_lock.gif/200px-Interface_lock.gif?e6c46
You can then resize or move your chat windows, minimap etc at your discretion. Remember to click the "lock" icon again to unlock the ability after you have done with your preferred customizations so you don't accidently change the sizes of your chat windows, minimap and such.
https://runescape.wiki/w/Interface#Resizing_windows
RS3 also provides us a very helpful way to save our preferred customizations with presets. We can save our current layout to not just one (1), but four (4) custom presets under the Settings -> Edit Layout Mode Interface. We are also given the choices to revert our layout back to New Player, Default among other standard layouts.
20-Nov-2023 15:47:18