Nowadays, messages are not seperated by SMS and MMS anymore. If a file like a picture is attached to the message, it is automatically an MMS. Sent and received messages are stored in conversations and saved on your Huawei device neatly. 

Android 10 | EMUI 10.0
Send SMS message -  Open  Messages
Send SMS message -  Tap on  Start chat
Send SMS message -  Choose a  contact  or type in a number
Send SMS message -  Type in a  message
Send SMS message -  Confirm with  Send
  1. Open Messages
  2. Tap on Start chat
  3. Choose a contact or type in a number
  4. Type in a message
  5. Confirm with Send

Huawei Instructions