Problem with installing WP

I followed this tutorial to install WP. Everything is fine until I must open wp-admin/install.php in my web browser. When I try to open it, it asks me, that do I want to save install.php to my computer. When I choose ‘open with firefox.exe’ then it opens new tab and asks again, that do I want save file to my computer or open it.
When I open https://variousart.pri.ee/blog/wp-admin/install.php displays it, that what you can see, when you click link…
And also…host, that I m using allows me to use php, mysql.