The Gecko theme after the installation has a search function in the header. In the standard configuration, this is a feature that allows you to search for WordPress content. You can enable or disable it (on desktop and/or on mobile) using the settings available in the Gecko Customizer. To get to them go to WP Admin -> Gecko -> Gecko Customizer -> Theme -> Header -> Header Search section.
If you are an Ultimate Bundle subscriber, you can expand its capabilities by enabling the New Search feature available through the Early Access plugin (PeepSo -> Config -> Early Access). Next:
IMPORTANT: This feature is in BETA version.