Can you please help me make these sentences sound natural? Thank you!

- I got suspicious when he offered a deal that seemed too good to be true.
- His mom got worried when he didn’t come back, so she went out to look for him.
- He got furious when he found out about the new deal.
- I cover my mug with a small plate to keep my chamomile tea warm.
- I cover my mug with a small plate to prevent my chamomile tea from getting cold.
- I cover my mug with a small plate so that my chamomile tea doesn’t get cold.
- He likes taking photos when it’s getting dark, but I, on the contrary, prefer taking photos when it’s getting light.
- They say men with prominent beards tend to go bad earlier.
- If you don’t refrigerate milk on a sunny day, it could go bad.
- If you don't protect your eyes, you run the risk of going blind sooner.

Question

Can you please help me make these sentences sound natural? Thank you!

- I got suspicious when he offered a deal that seemed too good to be true.
- His mom got worried when he didn’t come back, so she went out to look for him.
- He got furious when he found out about the new deal.
- I cover my mug with a small plate to keep my chamomile tea warm.
- I cover my mug with a small plate to prevent my chamomile tea from getting cold.
- I cover my mug with a small plate so that my chamomile tea doesn’t get cold.
- He likes taking photos when it’s getting dark, but I, on the contrary, prefer taking photos when it’s getting light.
- They say men with prominent beards tend to go bad earlier.
- If you don’t refrigerate milk on a sunny day, it could go bad.
- If you don't protect your eyes, you run the risk of going blind sooner.

Answer

Most of these phrases are very natural already. Well done!

Only two of them stand out to me, as being worth mentioning here.

- They say men with prominent beards tend to go bad earlier.
I think you mean to say 'bald'. If you fix this, then the sentence is fine.

- He likes taking photos when it’s getting dark, but I, on the contrary, prefer taking photos when it’s getting light.
This is not bad, but I recommend changing "on the contrary" to "on the other hand" as it's smoother, especially in casual speech. People do say "on the contrary" but it's usually in much shorter sentences - usually as a standalone phrase because it's such a quirky thing to say.