First, you need to be using a phone that is running at least Android "Marshmallow" (or newer) or be able to upgrade to it. Second, you will need the instructions I am including below. And third, you need a phone that has not been restricted by the manufacturer from making this change. Which does happen.
NOTE: If any of the steps are missing on your phone, or they don't work for you, then you have a phone that either has an older Android version or has been restricted by the manufacturer.
How to turn the "External" SD card into "Internal" storage on "Marshmallow".
NOTE: Please be sure you start with a blank SD card. It needs to be blank because when the card is converted to "Internal" storage, it will be formatted (wiped) and encoded (making the cards data only readable by that device).
1. Go to device “Settings”, then select “Storage”.
2. Select your "SD Card", then tap the “three-dot menu“ (top-right), now select “Settings” from in there.
3. Now select “Format as internal”, and then “Erase & Format”.
4. Your SD Card will now be formatted as internal storage.
5. Reboot your phone.
NOTE: If you don't reboot the phone, many things may not work correctly, so make sure you do.
How to turn the "External" SD card into "Internal" storage on "Nougat".
IMPORTANT NOTE: Be sure you start with a blank SD card. When the card is converted to "Internal" storage, it will be formatted (wiped) and encoded (making the cards data only readable by that device), so anything on it prior would be gone.
1. Go to "Settings", and then select "Storage & USB".
2. At the bottom of the list you should see the SD card's details, including the option to format it and make it "Internal" storage.
3. Once this is done, reboot the device and you can start running things from the card.
If you don't reboot the phone, some things may not work correctly, so make sure you do the reboot.
I won't say 'no' version of that particular manufacturer's phones can do that. That wouldn't be wise to say. However, I can say I have run into a lot of devices by that particular one that have this issue. No matter if you doubt it or not. It is becoming more and more common, with more and more manufacturers actually. Sad but true. There are a few reasons they do it, and I do get them, but I am of the belief that it is your device once you have paid for it (in full) so you should be able to do what you want with it. As long as it isn't a warranty issue.
Images won't help, I have done this on a lot of phones, and helped more on here with it, and if the options aren't there, the phone can't do it.
You do have the option of rooting the device. Personally I am so not a fan as it is a risk. It will totally void any warranty and doing it comes with actual risks, including bricking your device. However, should you wish to try something like that, you can post questions about it in the "Rooting, Jailbreaking & Unlocking" Forum. http/www.tomsguide.com/forum/forum-117.html