1. Close Old Tabs
For Close tabs Long press the tab button in the lower right corner. then tap Close all tabs. (also You can tap the Tabs button and long press Done to go to the same option.)
2. Clear Browsing History, Cookies and Data
First go to Settings > Safari, tap Clear History and Website Data. This Will Clear your all history and Cookies but Autofill Form data and Bookmarks will be stay.
3. Disable Unwanted Background Processes
To disable automatic downloads, go to Settings > iTunes & App Store and turn off automatic downloads for Music, Apps, Books & Audiobooks & Updates.
To disable Background App Refresh, go to Settings > General > Background App Refresh, turn it off. Or you can disable this feature for individual apps from the list below.
4. Reset Your Network Settings
If all else fails, try resetting your mobile network connection. Your saved Wifi networks will be gone.To Reset Network Settings go to Settings > General, scroll down and tap on the Reset. On the Reset page, tap Reset Network Settings.