Welcome to Yamaha Synth!

I almost bought Motifx7, but when i try the instrument the sound changing behavior very bother me.
1 it shut of all played notes when change voice on VOICE mode.
2. in PERFORMANCE mode i did not found easy why to change voice with out stop the arpeggio pattern

did i"m miss something on that instrument

Yes, you did!

The problem with deciding something doesn't work or has a strange behavior BEFORE knowing how to actually work the instrument is a problem. Thank you for the question.

In Voice mode each Program has complex routing from its 8 Oscillators (Elements) through its advanced Effects. Each Voice has two INSERTION Effects (an Element can be routed through one, the other, both or neither), this makes for very complex and very detailed programs at the Voice level, then you have two SYSTEM Effects (one for Reverberation and one for time delay Effects, Chorus - all Elements travel through these Effects) and finally the MASTER Effect (overall)... these are customizable and storable per VOICE.

If you are familiar with a recording studio think of each VOICE as having a patchbay full of cabling allowing intricate routing on a per Oscillator basis. Changing from one Voice to another would require ripping out all the patch cables.... So naturally there is an interruption in sound. This is not the MODE you want to be in for switching between programs. It is more a mode for construction and auditioning. An ALL NOTES OFF message is send if you send a Program Change (this is basic MIDI 101).

In PERFORMANCE mode you can recall multiple (4) Voices simultaneously, and in SONG/PATTERN MIXING modes you recall 16 Voices. And in these modes you can switch between them immediately... without and interruption in the sound.

Arpeggios can be assigned to a VOICE in any mode. The key to all of this is knowing which MODE allows you to do what you need. In the MIXING mode (so named because you can have a 'mix' of your favorite Voices, 16 of them recalled at once... all the RESOURCES, (effects, EQ, etc.,) are recalled when you recall the SONG or PATTERN setup... So switching between sounds is completely glitch free. Each is on a specific MIDI channel, and the numbered buttons [1]-[16] allow you to switch MIDI transmit channel as you require. You have 16 Insertion Effects activated (8 Part x2 Inserts each), the 2 SYSTEM Effects, and the Master Effect. The 8 PARTS recalling their Insertion effects can be controlled in real time via the assigned physical controller.

So by not knowing about the features and functions of the modes you might conclude (prematurely and incorrectly), as you did, that you cannot switch between the sounds you want to play - it is simply knowing which mode to be in when you want to do that. (Like concluding that an elephant is a small animal because you only touched/examined the tail)... The thing is much bigger than your first impression.

And since arpeggios (four arpeggiators are available) can be assigned in any of the modes, the two conclusions you made definitely are addressed in the other modes. It is easy enough to switch between sounds as necessary. Think of VOICE mode as your library of individual instruments... Think of PERFORMANCE as a basic rhythm section where you have four separate instruments to be played at once... Think of SONG/PATTERN MIXING as the full orchestra in the Recording Studio... because you are free to assign MIDI channels per the 16 PARTS as you require you can even switch between multiple PARTS Layered without any interruption in sound. You can hold one sound either with the keys or a sustain pedal while you switch to another and continue to play!!!

Also as you get involved you will see Yamaha has added some new and unique features for transitioning between sounds... XA CONTROL Expanded Articulation Control allows seamless transitions between any sounds, it is designed specifically to to increase transitions between the sampled Waveforms that make up a Voice, and is designed for the performing of the sounds with greater emulating response. But it can be used to switch between complete sounds as well.
Try the String orchestra Voice called "MEDIUM LARGE SECTION"... the [AF1] (Assignable Function 1) button switches between bowed string and pizzicato articulations... But it could just as easily transition to an entirely different instrument sound! This is up to you.

You can hold one sound, change articulation or switch Midi channels and play another without any interruption in sound. You simply have to spend a bit more time with this instrument before you conclude that this is not possible.
Voice mode is for auditioning and building your individual sounds
Performance mode and Song/Pattern Mixing modes are for performing and combining your selected Voices.

Hope that helps. Thanks for the question.