G'day paulliano, Welcome to Linux.org
In Terminal, type:
When alsamixer is opened, then you can:
press F1 key for help to see all the options you can use,
press Esc key to return to volume bars,
press F5 to see all volume bars,
raise the volumes by using the up arrow key, and move from bar to bar with the left and right arrow keys.
press Esc to quit alsamixer when you're finished.
and also read this
Use the right and left arrow keys to navigate through the sliders.
At the bottom of each slider you see either 00 or MM. Toggle these with the M key. MM means muted, 00 is enabled.
Use the up and down arrow keys or the Page Up/Page Down keys to control the sliders. Page Up/Page Down move the sliders in increments of five, and the End key resets to zero. When there are two channels controlled by one slider, Q increases the left channel and Z decreases. E increases the right channel, and C decreases.
Press F2 to see all the system information on your sound cards. If you have more than one sound card press F6 to display a sound card chooser.
The red arrow at the bottom of this pic shows MM.....which means that in this case my headphones are muted....if I use the right arrow to move to that column....and then tap the M key, that will unmute it
View attachment 19371
This link is worth a read
and this one
Thos links do not directly address your problems but they should give you an understanding of making adjustments/moving around alsamixer in Terminal.