Sebb's Sabbatical Contract

On the seventeenth of November, Sebb received an email with the draft contract from his boss. We had never seen such a contract before, where would we have? What we read sounded great. This was how we imagined it; starting in 2024, Sebb would deposit part of his gross salary into a so-called time value account, which would be secured against insolvency and then paid out during the travel period. We researched this online and concluded that the contract was written as recommended in the relevant forums. Should we still consult a specialist lawyer in labor law about this? And what would that cost?