Problem to install grav to my site

I try to install Grav +admin through Softaculous and succeed initially. But I could not see some pages in Admin for plugins, or themes. They display like broken with a giant G. I could not search and install other plugin or other themes. For this reason uninistalled grav.
I try second time to download and uploaded grav skeleton PINPOINT. But then I didnt have a clue what to do after that.
I read that I must run some command in command line, but I didnt understand where must I run this command!
I downloaded composer and I uploaded in my server of site. But I didnt understand again what must I do to install the grav,,,
I search in google, youtube, but nothing.
I deleted this again.
But I like grav and I would like to try again. Do you can help me, what must I do to install it in my website? Or if there is some tutorial for beginners like I am?
In Learn.getgrav.org I cannot find help for this...
Thank you from Greece.

@erevnitis, I'm afraid I do not get a clear image of your issue...

... succeed initially

What does this mean?

• Were you able to see the default website with Home and Typography?
• Did you have working Admin?

But I could not see some pages in Admin for plugins, or themes. They display like broken with a giant G.

How does that look like?

uploaded grav skeleton PINPOINT

As far as I know, there is no skeleton PINPOINT, not theme PINPOINT.

I read that I must run some command in command line

Where did you read that?

but I didnt understand where must I run this command!

In the shell of the machine on which you are installing Grav.

I downloaded composer and I uploaded in my server of site.

No need to do that, unless your are developing your own plugins.

Or if there is some tutorial for beginners like I am?

https://learn.getgrav.com are the only docs available.

Please be aware, Grav is not aimed at users without a base level of development skills or command line skills. Only in case you are fine with predefined themes and plugins which can be installed through Admin, you might get around.

If you have FTP access which I think most do, download Grav + Admin from https://getgrav.org/downloads and upload the unzipped files to the root of your www catalog.

I hadneed for any command line interactions or creating anything else but configuring the installed Grab site after I downloaded and uploaded the Grav + Admin pack

I used the files at https://getgrav.org/downloads that where not the skeletons pack which according what I can see also Includes configurations?

If the skeleton pack includes configurations maybe that's what creates the troubles your having?

I installed grav+admin with ftp in my server to xristianoi.gr. Initially I installed the unzip files as was with folder grav-admin. The site have error 403 and site/admin error 500. Second time I remove before the files, and after I transfer all files inside the folder grav-admin but not the folder grav admin.
Again I have the messages 403 for site and 500 for admin.
Do you have some idea?