I want to send a message to my girlfriend, but I don't know how to say it.

Just send some wing greetings at first according to the time until he answers you. For example, if you send a text message asking what she is doing, just pay attention. You can send a message and send it later if you don't reply. There are some greetings when you send them, but you can't use the tone of questioning. It's best not to get to the bottom of it. For example, if you don't reply to me, why don't you reply to my message?