After submitting a content, you still have 30 minutes to adjust it. After that, no further editing is possible.
Desktop / Laptop
To edit a post, click on "edit" in the lower right corner. After you have edited the text, you have to click on "save" below the text field.
Smartphone / Tablet
On mobile devices, the view is somewhat compressed to save space. At the corresponding post it is necessary to click on the three dots next to them. A menu will open where you can select "edit". After editing you have to select "save" under the text field.