Plugin won’t activate – cannot declare class (already in use)

Because WordPress already have class named Request

https://developer.wordpress.org/reference/classes/requests/

When creating a plugin or using boilerplate to generate, you should add prefix for your plugin name/class name, or avoid using very basic name.

Example:

class Wpse309780_Request
{

    function __construct(argument)
    {
        # code...
    }
}