How can I write two sentences in the same line on each other?

[sepisoad]

I think it’s better to give you an picture example:

how can i do this in libreoffice?

[Lupp]

You may use a frame anchored as character and formatted to your needs. The frame style may be reused. Under some aspects there will be a certain degree of tinkering needed.
ask70311FractionLikeTextInLine001.odt

[PYS]

Hi

LibreOffice has a feature for this:

• Check Tools▸Options▸Language Settings▸Languages▸Default Languages for Documents: Asian
• Type the concerned text (e.g. 1234), select it
• Format▸Asian phonetic guide▸type abcd in the Ruby text column▸Close

By default, the Rubies character style applies to Ruby text. You can adapt it to your presentation needs.

In the attached example I added the underlined and increased the font size. I also created the RubiesBase characters style to apply the same font size to the 1234 text.

Regards