httpd.conf is cached and no editing is succesful

I am going to use the WSL system on Windows10 to create a website. The distro is Ubuntu.

I put httpd.conf in /etc/apache2/conf-available

where there are these two lines (line 40):

Define SRVROOT "/etc/apache2"  ServerRoot "$  {SRVROOT}" 

When I try to start Apache it says that an error is found:

ServerRoot must be a valid directory (line 40) 

The fact is that I can edit the file, or even comment those two lines, or remove the httpd.conf file

but the error is issued every time I try to start Apache.

I suspect that files are cached.

How to avoid this kind of caching or solve the issue?