Thanks for posting at least basic descriptions with the code numbers. Too many people post numbers along with " Tell me what part to change because I don't want to make an effort " .

Be aware that a detailed code description is critical to efficient diagnosis. For example, the extended description for " P0100 mass air flow sensor " might include : MAF voltage out of range low / MAF voltage out of range high / MAF voltage erratic / MAF voltage implausible. This info would be found in a service manual / better scan tools. Low end scan tools tend to give the short generic description that leads to random parts replacement.

Hang a volt meter on the MAF output and have a look. Don't 100 % rely on scan tool readings, sometimes the ECM will substitute a plausible value during a failure that the scan tool will pickup.

If this is a W210, they have issues with under hood grounds.

Also if W210 , the MAF has a 12 volt source from the cars wiring to power it up the electronics and a 5 volt source from the ECM that is modified for MAF signal out.