It is not clear in which transaction you are at this point: "When I switch to the material components and enter the component number (the same number as "main" materiál) together with its amount needed I cant enter the valuation level/batch. When I go back to the item overview and then back to components overview I can actually enter the valuation level/batch."
In some transactions the presentation of fields is depending on other entered data. So you can only get those fields by clicking Enter/continue, clicking the check icon or by leaving the screen and coming back. Only in that moment SAP reads your entry and is looking up the the material master to find out whether it is batch managed or split valuated.
(other people would be confused if those fields would always be present even they do not have batch management or split valuation active, and entries in such fields could then create error cases too)