breake pedal wheels soft sometimes.. Any idea?

Hello! more problems to fix = )

Sometimes when im pushing the break pedal if feels soft when the car is still and not driving away then its better when driving but not 100%. I could also hear a air sound in the pedal sometimes. the break fluid is ok!

[Mazda RX-7 SA]

Have you perfectly vented the system?
To get out all air.
When was the last change of brake fluid?

Nope but i asked some mechanic today and maby they said the breake cylinder.

The breake pedal today was breaking but the pedal was really low down!

[Mazda RX-7 SA]

I would say:

1. Change the brake fluid and perfectly vent the system.

If this doesn't solve the problem it could be the brake master cylinder.