Hi Norbert78,
Welcome to Affinity Forums :)
There's quite a few ways to do this. Here's some:
1. draw a small rectangle over the point of the i then go to the top of the Layers panel and change the Blend mode dropdown from Normal to Erase. This will hide everything below the rectangle, including other layers. to force it to be applied just to the text, drag the rectangle layer over the text layer in the Layers panel. The text remains editable and you can always disable or delete the rectangle layer to get the point back.
2. If you don't need to edit the text anymore (since it's part of a logo) you can convert the text objects to shapes, selecting the text and going to menu Layer ▸ Convert to Curves. Then go to the Layers panel, click on the arrow inside a circle on the left of the thumbnail to expand it, select the i, change to the Node Tool and drag a marquee around the point of the i. Press delete on you keyboard to get rid of the point definitely.
