Hi and welcome to the forum
It would help if you could describe to us what you did last time that led to that problem.
Can you give us the content of the .htaccess file located in your htdocs folder (if it exists)
open it with file manager (monstaFTP)
copy and paste here
and a screenshot of the htdocs folder
Did you perhaps delete the default .htaccess file?
So if you don’t have a .htaccess file (I repeat if you don’t have that file)
create a new one with this content
##################################################
#
# DO NOT EDIT THIS FILE DIRECTLY
#
# Create a new .htaccess file in your htdocs
# directory (or example.com/htdocs/ directory)
# to add your own rules or override these rules.
#
##################################################
DirectoryIndex index.php index.html index.htm index2.html
ErrorDocument 400 https://infinityfree.net/errors/400
ErrorDocument 403 https://infinityfree.net/errors/403
ErrorDocument 404 https://infinityfree.net/errors/404
ErrorDocument 500 https://infinityfree.net/errors/500
ErrorDocument 503 https://infinityfree.net/errors/503