I right-clicked the midi track fader but no any options about "reset"....

By reset, I mean manually adjust the level a level that makes sense.

parco
I right-clicked the midi track fader but no any options about "reset"....

Are you using Simple Instrument Tracks or the traditional split MIDI/Audio combinations for your synths?   If it's the latter, try adjusting the audio track, not MIDI.  Also, double-clicking any fader should reset it to its default value - out of the box that's 0dB for audio and 101 for MIDI.
 

In the past, I have resorted to copying the track data to a new track while filtering out envelopes.