My laptop is a 2018 model MacBook @Pro. I used the VMware fusion to install a window 10 virtual machine on a SanDisk 200GB Ultra micro sd card. I am able to use the machine to handle paperwork and surf the internet. But after I downloaded the Arma 3, I was not able to play it because the response time is too long. If I move my mouse, after more then 20 seconds, the mouse icon starts to move. And it took a very long time to load the game.
How can I fix it? What is the cause? Should I but a hard drive install of using this sd card?
I assume that the SD card simply cannot handle the required I/O. So yes, a HDD/SSD will most likely help, but I can't tell you whether the VM's video performance will be sufficient for the game. You will have to test this.
I suggest you move the VM to either your internal SSD or an external SSD connected via usb 3. They're relatively cheap nowadays, cheaper than a VMware Fusion license for 240GB. If I try to run Windows 7 era DX9 games I get great performance with a Fusion VM. Just as fast as running in bootcamp. This is on an i5 iMac 2013 with Nvidia 750m 1GB graphics. Newer games require me to use bootcamp. You can even clone a Windows VM to an external SSD using Minitool Partition Wizard 10 which is free for personal use so I can boot off Windows 10. I did this to run Windows 10 Steam games on an external SSD in bootcamp.
As the others noted, there's two pieces to this puzzle - storage and video performance. SD cards are slow, so moving the VM to the internal drive (fastest) or to a USB-C 3.1 (not 3.0) external SSD (bit slower, but still ok), will help the storage piece.
For the video piece, it depends on which MBP you have - if it's a 13 without a discrete graphics chip, it may be too slow to run the game.