Problem 1
- Root composer.json requires bitfumes/laravel-multiauth ^5.2 -> satisfiable by bitfumes/laravel-multiauth[5.2.0, 5.2.1].
- bitfumes/laravel-multiauth[5.2.0, ..., 5.2.1] require laravel/ui ^2.0|^3.0 -> found laravel/ui[v2.0.0, ..., v2.5.0, v3.0.0, ..., v3.4.6] but it conflicts with your root composer.json require (^4.2).

Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.
You can also try re-running composer require with an explicit version constraint, e.g. "composer require bitfumes/laravel-multiauth:*" to figure out if any version is installable, or "composer require bitfumes/laravel-multiauth:^2.1" if you know which you need.