Two filtered dates in one single visual

We work in the backend with a star chart which we have integrated into our dashboard via the SQL server. Here we can set different filters.

- Goal: We want to display Factory Installation Start and Factory Installation End in a single visual (e.g. Gantt chart).
- In our SQL-Server-star chart, there is a date table on one side and a table that breaks down the dates for different milestones (e.g. Assembly Start & End, Factory Installation Start & End, etc.) on the other side.
- The date of the date table and the milestones of the second table are linked to each other by IDs respectively.
- However, in a visual like a Gantt chart, the date cannot be filtered in FI Start as well as FI End. If we try to do this, we will get the same value twice in the visual (e.g. 2x FI Start).

We have also already built two new tables with a DAX function and used each of them as sources for the FI start date and FI end date, which did not work. Power BI still accesses the SQL server data from the backend.

Can you guys help us solve this problem?