PF: Can periods of inactivity due to the pandemic of COVID-19 and prolonged strikes at a university be considered and deducted as career breaks?

This has to be properly documented, just a statement is not sufficient. There needs to be proof that the organisation was shut down and the employees were suspended during the pandemic and strikes. In particular, the exemption for the period of university closures due to COVID can only be applied if the fellow was not under contract with the university during that time. If the fellow continued to be paid, that period must be counted as research time. Ultimately, it is up to the hosting organisation to verify the eligibility of the fellow.