通问

to mutually send greetings / to communicate / to exchange news

to go through / to know well / (suffix) expert / to connect / to communicate / open / to clear / classifier for letters, telegrams, phone calls etc

classifier for an activity, taken in its entirety (tirade of abuse, stint of music playing, bout of drinking etc)

to ask / to inquire

to ask; to inquire

common questions / general questions