Trying to regain access to a wordpress based website

My Dad has a website based on wordpress, he went into the wordpress dashboard and modified the home page incorrectly appending an extra level to it, then when he exited it made changes resulting in website being messed up and more importantly the login to wordpress has disappeared not allowing him to change it back.

I manually fixed the url to display the wordpress dashboard login, yet even when login it doesnt work, it takes be back to the wrong page.

I don’t currently have access to the wordpress database but I do have access to the files generated from the database so my plan was to edit the correct file to set the home page path back to what it should be, hoping that will then allow me to get into WordPress dashboard.
But I have very little knowledge of WordPress, anyone help me here please.