It wasn't until I lived on my own that I was surprised at the variety of items at the 100 yen shop. It wasn't until I lived on my own that I was surprised at the variety of items at the 100 yen shop.

It wasn't until I liveing on my own that I was surprised atdiscovered the variety of items at the 100 yen shop. It wasn't until living on my own that I discovered the variety of items at the 100 yen shop.

"Discover" is giving a similar feeling of "surprised", and makes the sentence sound more natural.

If you are looking for a suitable size of photo frame, you could choose from postcard size to A2 poster size with three color variations. If you are looking for a suitable size of photo frame, you could choose from postcard size to A2 poster size with three color variations.

If you are looking for suitable size ofa photo frame, you could choose from postcard size to A2 poster size with three color variation. If you are looking for a photo frame, you could choose from postcard size to A2 poster size with three color variation.

"Suitable size" is redundant because you mention the size variety later in the sentence. You could also try "any size photo frame" instead.

I'm was really surprised when I findound an A4 clear folder size which is bit larger than A4 size. I was really surprised when I found an A4 clear folder size which is bit larger than A4 size.

Some customers including me wonder how to display A4 clear folders which we bought at the museum shop or the anime store. Some customers including me wonder how to display A4 clear folders which we bought at the museum shop or the anime store.

I'm not sure what you are trying to say here, but it sounds like the larger-than-A4 folders are really popular, and solve a problem that you and other customers have. In which case: "It's a common challenge for me and many people, to get a folder that fits collectable items properly."

One of the most strange items at the 100 yen shop would be a kind of Japanese name seal called "Hanko". One of the most strange items at the 100 yen shop would be a kind of Japanese name seal called "Hanko".

One of the most strangest items at the 100 yen shop would be Japanepersonalised name sealtamps called "Hanko". One of the strangest items at the 100 yen shop would be personalised name stamps called "Hanko".

Even though it is used as an alternative way of signatureing when you pick up a parcel at the door or create new bank account, you can choose from thousands of family names and buy it without any identity verification. Even though it is used as an alternative way of signing when you pick up a parcel at the door or create new bank account, you can choose from thousands of family names and buy it without any identity verification.