[Support request] How to correct font size of excerpt (otherwise it display huge h1 and h2 texts)

Hi there, I’m using dispatch theme + wp show post pro.
My problem is that – when a text is in h1 or h2 – the excerpt is displayed in that font size, causing big design problems
You can see an example here :

https://ibb.co/HGpbPrf

how can I set up Wp show posts in order to transform the text it displays in the excerpt so even h1 or h2 appears as a normal paragraph text ?
thank you