To make your font size smaller or larger:
Google is rolling out a new option where users can now pinch-to-zoom to change the font size in Google Messages for Android. The functionality is quite straightforward and starts by opening any thread. Pinching out with two fingers increases most text in the current window, though the app bar stays the same.
On the bottom-right corner, you should see an “Edit” button. Go ahead and tap that. This will, unsurprisingly, open the Quick Settings Edit menu. Modifying this menu is super simple and intuitive: just long-press and drag icons to where you want them.
Add a Toolbar to an Activity
To create your own toolbar, click "New toolbar…" from the toolbars menu. Use the file picker to select a folder on your computer. When you press "OK," the toolbar will be added to your taskbar. Click the ">>" icon next to its name to view the current contents of the folder it points to.
The body text size in Material Design is 14sp. You should think of this as the normal font size, and basically everything else a variation on it. For instance, while 14sp is the default text size when the text can be quite long, when there's only a small modal with a bit of text, it's 16sp!
How do I change the font size on my device?