[Solved] Conflict with a composer

@fpbb,

Use this CSS code it should solve the first issue: 

.wpd-field-comment, .wpd-form-foot, #wpdcom .wpd-form .wpdiscuz-textarea-wrap.wpd-txt  {
    width: 100% !important;
}

Put the code in the Top Admin Bar > Customize > Additional CSS > "Additional CSS" textarea, save it, delete all caches and check again. 

Please don't forget to press Ctrl+F5 (twice) on the frontend before checking.

Beside, comments are being displayed on home page although I unchecked the option.

Please follow the steps below: 

1) Make sure the “Discussions” admin-box is allowed using “Screen Options” in “Edit Page” admin page:

2) Find the “Discussions” admin-box below and uncheck the “Allow Comments” option.