Huawei Mate 10 Slowing Down

I have just received a new Huawei Mate 10 from work, I set it up using my previous Google Account details and install all the usual apps onto it. It ran like a dream, it was so fast. I put the microSD Card from my SGS7 into it when I got home. I noticed that the next day, it was running extremely slow and would crash at times too. Any ideas what could cause this?

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