Main Menu Very Slow, But In-Game Is Not

For Some Odd Reason, The Main Menu For Me Is So Slow, Even Though My WIFI Works Well. Hosting A Custom Game Is Impossible! When I Tried To Start It, It Kicks Me Out And Says “Not In A Custom Game”. However, When I Do A Quick Play Match Or Any Kind Of Match, The Game Goes Smooth And Does Not Lag At All. Idk Why This Is Happening, But If You Have A Suggestion, It Would Be Appreciated To Tell Me. Thanks!