For playing piano with chords --> How do you change Key from A Major to C Major?

Q. ok.. so A major has three sharps.. yea? F,C, and G.
C major has no sharps.

if i my music piece says E(from A Major) and Fmaj7 (beginning of C Major) then what additional chords I should play between these chords to make a smooth transition?

WikiHow website provides some information about changing keys but I had no idea what it was talkin about.. its directions were confusing..

So can somebody provide a good explanation, please?

A. When you say E and Fmaj7 do you mean E major (E G# B) and then Fmaj7 (F A C E) or F#maj7? I just want to make sure. I will write back if you supply further information.

One simple progression would be:
E major (E G# B E)
Fmaj7 (F A C E)
G13 (G F B E)
C (C E G C)

Original Question

When playing a 9th, 11th or 13th chord is it better to omit certain notes?

Q. For example, if I play a G11 chord is it better to omit the 9th or keep it in?
Another example is if I play a G13 chord should I omit the 9th and 11th or keep them in?
Is it better to keep them in the chord for flavor or does it matter?

It's not really a problem keeping notes when playing piano chords but for guitar I only have the use of my left hand and a restricted space to play those notes.

Is it better to omit or keep certain tones in the chord?

A. You need the root.
You need the third to tell you the quality of major or minor.
You can omit the 5th of almost any chord.
It's usually best to have the 7th if possible as that indicates quality of diminished, half-diminished or major 7th
In a 9th chord you need the 9th. In a 11th or 13th you can omit it.
In a 11th chord you need the 11th, in a 13th chord it's usually better to omit it.
It's usually best to double the root because that way it's more clear what the chord is supposed to be.

Original Question

help with chords, please?

Q. my friend wnats me to play in his band, and he gave me some chords to play, but i cant read the guitar chords, can someone help me?

How do I play these on the piano:
Aaad9
C5
Bb5
Asus4
Absus2
Dm9
G13
CM9
G7
G7#5
Bb7
Dadd9

thanks

A. Ill tell ya what notes to put your fingers on

A add9 : A, B, C#, E
C5 : C, G
Bb5 : Bb, F
Asus4 : A, D, E
Absus2 : Ab, Bb, Eb
Dm9 : D, F, A, C
G13 : G,A,B,D,F
Cm9 : C, Eb, G, Bb
G7 : G, B, D, F
Bb7 : Bb, D, F, Ab

Original Question

Title : For playing piano with chords --> How do you change Key from A Major to C Major?
Description : Q. ok.. so A major has three sharps.. yea? F,C, and G. C major has no sharps. if i my music piece says E(from A Major) and Fmaj7 (beginning...