Like how long it takes to get a advanced bros.move???

it took me like a whole day to advance 1 bros.move
thats it!!

tell me how long it took you to advance 1

Keep doing the move over and over agin. Sooner or later it will become advanced.

What does advancing the moves even do?

advance moves do extra damage, and i know because i use Bounce Bros. tons, in like 10 min it was advance.

It takes 20 "Great!" commands to get the Advanced command for Splash Bros.;
10 for Swing Bros.;
32 for Chopper Bros.;
20 for Fire Bros.;
8 for Bounce Bros.;
43(?) for Knockback Bros.;
21 for Cyclone Bros., and
24 for Thunder Bros.

In addition, Splash Advanced does massive damage to a spiked enemy;
Swing Advanced lets you steal items;
Chopper and Knockback Advanced allow you to hit multiple times;
Fire Advanced pools all the fireballs into one for one massive hit;
Bounce Advanced hits two enemies,
Cyclone Advanced makes the enemy hit dizzy and does extra damage, and
Thunder Advanced hits one enemy and reduces its POW.

By the way, mariosuperstarsaga, please quit posting links to that page...

But how do you activate them? I get the advanced icon but can not change how the move works.

quote Eraser

But how do you activate them? I get the advanced icon but can not change how the move works.

Do any of those Bros. attacks on mode 1 or 2 and you'll see an exclamation point appear over Mario or Luigi's head (depending on which bro had the "Advance" earlier for that Bros. attack), then press A if it's Mario or B if it's Luigi. The rest, you'll be able to figure out yourself.

If you have trouble understanding what I mean, you can always look at a walkthrough to find out how to do the advanced version of each Bros. attack.

when i fight a boss sometimes i advance......

That's probably because you used the move a lot against the boss.