The way to understand what's happening is to think about how this would work if you were doing this manually, working with a selection. When you assign text to a Range
that's like typing it in, as you'd expect. The second line of code, inserting the image, is like selecting the entire cell (in this case) then inserting the image: it replaces what's in the Range. When working manually, if you had selected the entire cell, you'd press Right Arrow or click at the end to put the focus after what had been typed.
The same principle applies when using a Range
object: it needs to collapse in order to add something to it.
The following code example demonstrates this. It also highlights how the code can be made more efficient by assigning the table and the target range to objects.
Dim tbl As Word.Table 'or As Object if using late-binding
Dim rng As Word.Range 'or As Object if using late-binding
Dim chrCount As Long
Set tbl = oDoc.Tables(1)
Set rng = tbl.Cell(zeile, spalte).Range
rng.Text = "test"
chrCount = rng.Characters.Count
'Get the end of the cell content
Set rng = rng.Characters(chrCount - 1)
rng.Collapse wdCollapseEnd
rng.InlineShapes.AddPicture path_to_image