Printer Ink Cartridges & Print Quality

Hello.

I have a HP Smart Tank 720 ( 6UU46A ).

I received it, I fill the tanks with ink and I received a phone call of 20 minuts. When  I came back to put the PrintHeads

Cartridges I can notice air inside 2 of the 4 ink pipes (blue and red), they was all 4 full of ink just before the phone call. I decided to contact the support, but no answer. I was puting the printer off for the night, of corse, and the printhead kart gone to the full right side of the printer. When I open in the morning the printer to check the pipes, now the blue and red ink pipes are with less ink (more air) and the black now is almost empty, the orange is still full of ink.

My problem is this one, and I'm searching some official informations about this printer :

1 / Is a normal use of the printer to have air in the ink pipes ?

2 / Is the valves at the end of the ink pipes, before the printheads  needs to be hermetic ?

3 / If there is air in the pipes, is this air is expulsed by the printer, or it go inside the cartridges and lower the ink level of it ?

4/ If the answer is yes, is this lower the life of the product ?

Now I put the cartridges to test the hermetic part of the ink circuit, and air is going inside the 4 ink pipes all times now, when the printer dont print.

5/ Is it normal to have air going inside the ink pipes all times ?

Thank you for any official answer !

EDIT : added photos 

EDIT 2 : someone removed my pictures, maybe because of the serial number, but they whas showing a level very low of ink in the pipes, almost no black ink in the pipe, red at the half, and blue and yellow at the 3/4 only. This happened before to put the cartridges, and mmafter another air purge and some print test the air is going again and again in the pipes. The only picture still accessible here just show what happened after 5 minuts...