Any time you connect through a VPN, there are bound to be some losses in speed. This is because instead of simply going from mobile device -> website/service -> mobile device, there are extra steps that need to be completed. When connecting through a VPN, your device must encrypt the data, send to VPN, from there it goes to the website/service and back to the VPN, then back to your device, then it needs to be decrypted before it can be displayed. Of course, the further you are from the servers, the longer this will take and the higher the losses will be.
If you are experiencing loss in speed, try the following steps:
First, make sure that your Android and Internet work fine when the VPN is OFF. If not, it may be a problem with your connection through your mobile network or Wi-Fi.
If your speed without Hotspot Shield is fine but it slows down when Full protection is ON, please try Smart Mode.
Also, please try switching between mobile network and Wi-Fi, or use different Wi-Fi.
If problem still exists, go to Android's Settings > Apps > Hotspot Shield and tap Clear data & Force stop. After that, tap Hotspot Shield icon to launch the app.
If nothing helps, please go to this link and submit a ticket to support team.