iPhone 11 Pro Max texting problems

For a few months now, when I try to send a text, my device is very unresponsive! I have to wait after each number I type, as it freezes. Then when I try to send it, the Send arrow is often not green (ie ready to send) so I can’t send the message. It’s so frustrating and infuriating! Can take me hours to get one text message sent! If it sends at all. I also often completely lose the text message I’ve just written, as I think I’ve sent it, then it comes up blank and no message was sent. Any suggestions as to what’s going on or how to fix this non-responsiveness??