How to increase body font size for mobile screen

I am using Sparkling theme and Google console has reported following errors in mobile usability report:

Text too small to read
Clickable elements too close together

The errors are general for the whole website because these properties are same on every page of my website. However, Google has mentioned the following URL in the example:

I tried to add media query for increasing the font size in the custom CSS but did not work. Please help resolving both of these issues as I believe it will affect the SEO of my website adversely.

Hi there

Can you please provide a more detailed report? which elements are closed to each other? which text is too small? we can change them but I need to know where exactly this is happening

Clickable elements too close together
Touch elements, such as buttons and navigational links, are so close to each other that a mobile user cannot easily tap a desired element with their finger without also tapping a neighboring element. To fix these errors, make sure to correctly size and space buttons and navigational links to be suitable for your mobile visitors. Read more in Size Tap Targets Appropriately…

Text too small to read
The font size for the page is too small to be legible and would require mobile visitors to “pinch to zoom” in order to read. After specifying a viewport for your web pages, set your font sizes to scale properly within the viewport. Read more about font size best practices in Use Legible Font Sizes.

No further details have been provided by Google. I assume its about both navigation links text and body text because the font size is almost the same for both on mobile screen.