What is wrong with DW?

• Which version of DW do you have -- Help > About Dreamweaver?
• Is your site defined? 
• Does your site folder reside on your primary hard drive, not cloud drives like DropBox or Google Drive?
• Please ensure your computer meets or exceeds the minimum system requirements to run Creative Cloud + OS + your version of DW.  See links below.
  - https://helpx.adobe.com/creative-cloud/system-requirements.html
  - https://helpx.adobe.com/dreamweaver/system-requirements.html

Adobe expects users to have the latest software and operating systems, no more than 2 versions back.  Failing that, your experience may not be terrific but DW is just a glorified code editor.  It should not be so slow that you can't use it.

Bad code can cause unusual behavior.  As can a corrupted Preferences file.

Validate code and fix reported errors.

HTML - https://validator.w3.org/

CSS - https://jigsaw.w3.org/css-validator/

Restore Preferences

- https://helpx.adobe.com/dreamweaver/kb/restore-preferences-dreamweaver.html

I am not a system specialist, but using an Operating System much more contemporary than the hardware, is never a guarantee of flexibility of use.
In fact, OS are developed according to the technology of the moment. So if the computer is 10 years old, it was operational and in adequacy with the OS of 10 years ago.
this said, it will work, but the resources will not be optimal and this can be translated by latencies during the use, until becoming complicated according to the programs. And Dreamweaver is not without worries on this side.

then

As for the use of accented characters, make sure you use a UTF-8 encoding and your worries should disappear.
From the menu File > Page properties
and in this dialog box, choose, Title / coding, you will have the possibily to change the page encoding to UTF-8

all the others settings by default, should be fine