I downloaded membership app and now i can't log into my website and change/edit

What membership app?

You wrote

“…I can just log onto my website and make changes”

so why not just go and delete the membership app plugin?

Sorry I CAN NOT log onto my website like i used to be able to and be able to edit it. It only allowed me to be the admin member. the app is called membership .

Ah ok. It sounds like there’s a conflict between the plugin and your theme or another plugin.

So is it this plugin? https://www.ads-software.com/plugins/membership/ They have a free and a “Pro” version, and the Pro version is only $19. For that price, you’ll get good support from WPMU, which would seem well worth it.

For the free version, you *might* get some help by posting on the plugin’s support forum.

I found these instructions in the WordPress Codex for disabling a plugin in your situation:

How to deactivate all plugins when not able to access the administrative menus?

Sometimes it may be necessary to deactivate all plugins, but you can’t access the administrative menus to do so. One of two methods are available to deactivate all plugins.

Use phpMyAdmin to deactivate all plugins.

In the table wp_options, under the option_name column (field) find the active_plugins row
Change the option_value field to: a:0:{}

Or reset your plugins folder via FTP or the file manager provided in your host’s control panel.

Via FTP or your host’s file manager, navigate to the wp-contents folder (directory)
Via FTP or your host’s file manager, rename the folder “plugins” to “plugins.hold”
Login to your WordPress administration menus (/wp-admin)
Via FTP or your host’s file manager, rename “plugins.hold” back to “plugins”

(From this page)

I hope one or the other of those suggestion might help.