Hi Ruben,
For one-way SMS with Azure MFA in the cloud (including the AD FS adapter or the Network Policy Server extension), you cannot configure the timeout setting. Azure AD stores the verification code for 180 seconds. https://learn.microsoft.com/en-us/azure/active-directory/authentication/multi-factor-authentication-faq
Aside from improving the connection itself, there are some potential solutions I can think of:
You can set "remember MFA" for trusted devices so that users aren't prompted and don't have to go through this as frequently.
If you are using Phone MFA you can adjust the timeout by adding a recording. One way to do this as a workaround is to record a message that is 18+ seconds long long and upload it as "Greeting(Standard)." This will push the timeout long enough for it to route through the phone system and have enough time to press # to verify. See instructions here: https://learn.microsoft.com/en-us/azure/multi-factor-authentication/multi-factor-authentication-whats-next#custom-voice-messages