heater not working properly

You have two issues but they are the same type of part. Here is a guide that talks about the defrost issue:

https://www.2carpros.com/articles/air-vents-stay-in-the-defrost-position

Basically the mode door actuator changes the direction of the air. When it fails the vents default to defrost because it would be a safety issue if you have no defrost and the windows fog up.

The air only blowing warm on one side is due to a different actuator which is the blend door actuator.

Here is a guide that helps with that:

https://www.2carpros.com/articles/replace-blend-door-motor

Lastly I attached the process from the manual to replace these. For the blend door, you are going to want to replace the side that is not blowing warm when you have it set to warm temperature.

Let us know if you have questions. Thanks