Hide media urls from public

Hi,

When I upload an image, for example “picture1” that I want to use on my website,
it will create a link “mywebsite.com/picture1”.
Now if someone would type this link, it just shows my header and the image under it, which looks very unprofessional. I would like to “disable” all these urls.

It is only myself (administrator) that can edit the website, the normal visitors cannot edit or upload anything.

I have tried looking up how to fix this but cannot find it.
I’ve tried
– media library/settings
– I cannot find “attachment display settings” which some guides refer to
– plugins to restrict content per role (doesn’t work for media)
– add the code to functions.php / in my options it is set to “none”

None of these things work. When I type mywebsite.com/randompicturename it will show that image.

(I can’t link my website as it’s hosted locally)