Hi @IBN
You add two different accounts (one work account and personal accounts). At this time you cannot add two different work accounts. This is currently be implemented but there is no date determined when it will be implemented:
Enable usage of multiple Teams accounts at the same time (feedback)
https://feedbackportal.microsoft.com/feedback/idea/d256e0f6-262e-ec11-b6e6-00224827bbc2
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If this is helpful please accept answer.