Running an older device with Android 5.1.1 (Lollipop) doesn't mean you're stuck without the latest apps. Whether your device didn't come with the Play Store or you accidentally deleted it, you can manually install it using a verified APK. Where to Download: Best Verified Sources
Do not search random websites. Use reputable APK repositories that verify signatures to ensure the file is not tampered with. Running an older device with Android 5
Follow these steps to manually install the Google Play Store on your Android 5.1.1 device: Can I update the Play Store beyond version 38 for Android 5