You need to provide more information.
At it's simplest, the turnover you require is €192k
192k@ 26% margin = €50k
But variable costs usually rise with turnover. If your turnover rises to €300k, I would expect your variable costs to rise.
If you want to give more information abou the context and the actual costs, I might be able to give a better answer.
It's not always easy to categorise a cost as wholly fixed or wholly variable.
For example, rent is a fixed cost. But if your business expands, you will need a bigger premises, so you will pay a higher rent. Wages may be fixed for a particular level of production, but may rise if you need to take on more employees or if you pay commission.