The limit is not set, however chancellor must be voted in every 46 to 48 months.

However your second point is not correct at all, Germany had made their beurocracy specifically in such a way after WW2 that one person cannot dictate/rule the country. Every decision must pass through appropreate ministries first. This is one of the reasons COVID vaccination rollout was so slow in the beginning but after all the "approvals" were met they are vaccinating ~1m people a day. Chancellor in Germany is not even close to power of President in US, for example.