Clear app data · Delete cache (including search suggestions, direction searches, map tiles, and activity page content stored on your device) · Delete cookies.
1) Clear the iOS application data. You can do this by opening the Google Maps app and going to Settings -> About, terms and privacy -> Clear application data.
When the navigation becomes laggy, I go to Settings - 'About, terms & privacy' then I opt for Clear application data. Navigation gets back smoothly.