You can pause your account activity at any time by turning off AutoPilot for your goal from the Home screen. If you have multiple goals set up (ie. Savings & Pay Off Debt), you'll need to turn off AutoPilot on both to stop all activity.
When you're ready to start again, just turn AutoPilot back on for your goal(s). Your goal will not backdate any contributions while your goal was paused, so you don't need to worry about a huge sum of cash coming out of your checking account when you resume.
However, transfers already initiated that were not canceled individually will still go through.
Additionally, turning AutoPilot off will only stop your savings automation, it will not pause payments from sending out. You can pause your monthly payments in the app as well: first, open the app and log in, then click on your Pay Off Debt goal. Select which payment you'd like to pause and then click the three-dot menu in the top right corner. Here you'll have the option to pause your payment from sending.