was just given this. You must first long press email to highlight then you can press other emails to batch delete.
Here is a quick tutorial: How to Bring Back the Delete Button in the New Gmail for Android
Steps:
Here's how to get the trash can back on your toolbar:
1. Press the menu button on your phone, and select settings from the pop-up menu.
2. Tap "General Settings," then tap "Archive & Delete actions" at the top of the menu.
3. Next, you'll see a pop-up menu with "Show archive only," "Show delete only," and "Show archive & delete." Archive only is the default. Select the one you prefer. I like "Show archive & delete," because options are good things to have.
4. Press the back button to go back to your message view.