Step 1) Delete your current bedrock_server
Step 2) Go to this link and download the UBUNTU version https://www.minecraft.net/en-us/download/server/bedrock/
Step 3) Upload the new bedrock_server to your server
Step 4) Login with WinSCP or FileZilla
Step 5) Change the file permissions to 0755
Step 6) Start your server, and you're done