Good news, a nice day, a kind message. "I'm happy" is fine, but fluent speakers pick a different line for a little bit pleased and absolutely delighted.
Way 1 · best default
Clearly happy about something specific. Natural with friends, family and at work.
Examples
I'm really pleased with how the photos came out.
I'm really pleased you could make it tonight.
In a conversation
A: How did the exam go?
B: I got a B! I'm really pleased.
Way 2 · kind reply
Gentle happiness about someone else's news. The polite, warm reply when things are going well for them.
Examples
Your mum's feeling better? I'm glad to hear that.
I'm glad to hear that the move went smoothly.
In a conversation
A: The new job's going really well, actually.
B: Oh, I'm glad to hear that.
Way 3 · no reason needed
You feel happy in general today, maybe for no special reason.
Examples
The sun's out and I'm in a good mood.
Ask him now. He's in a good mood after lunch.
Common mistake
Not: I'm in good mood today.
Say: I'm in a good mood today.
"Mood" needs "a" here: "in a good mood", "in a bad mood".
Way 4 · small thing, big smile
Something small and kind made you very happy: a message, a compliment, a surprise coffee.
Examples
You brought me a coffee? That's made my day.
Thanks for the lovely message. It's made my day.
Way 5 · big news
Very happy about big news. Common for jobs, babies and wins, and fine at work too.
Examples
I'm thrilled to be joining the team.
They're getting married? I'm thrilled for them.
Common mistake
Not: I'm very thrilled.
Say: I'm thrilled.
"Thrilled" is already very strong, so "very" sounds odd. For extra, say "absolutely thrilled".
Way 6 · on top of the world
Extremely happy. Friendly and very British, for the best news of the year.
Examples
I got the flat! I'm over the moon.
She passed her driving test first time and she's over the moon.
In a conversation
A: So, did they say yes?
B: They did! I'm over the moon.
Read the moment, then choose the way that fits it best.
What a translation app gives you, and what people actually say.
Not: I'm happy for my new job.
Say: I'm really pleased about my new job.
"Happy for" is about other people's good news ("I'm happy for you"). For your own news, use "about" or "with".
Pick one and practise it in a real conversation. Save the ones you want to remember.
