TI'm tired of this kind of thing.

It feels unnatural not to include the pronoun "I" in this narrative style passage. Just for illustrative purposes, a common alternative is: "I'm so sick of this kind of thing."

Fortunately, ithis is the first time I've caome across this kind of thing.

It sounds more natural to use "this" instead of "it" here.

I changed your sentence to "...the first time I’ve come across this kind of thing" because present perfect in English expresses a new, relevant experience: something that’s just happened and now affects the present.

In Chinese, I think your sentence would be: “这是我第一次遇到这种事情。”
This sentence avoids both 了 and 过, and here’s why:
You don’t use 过 ("遇到过") because 过 talks about past experience in general, something that has happened before — which contradicts "first time."
You don’t use 了 for completed action ("遇到了") because that just means the thing happened and is over — it doesn’t highlight that it’s a first-time experience or that it’s still relevant now.
You also don’t use 了 for change of state ("遇到了") here, even though technically this is a change — because "第一次" already shows the change: this is a new experience that has just become true. In Chinese, when that change is obvious from context, 了 isn’t needed.
So in Chinese:
“这是我第一次遇到这种事情。” (no 了, no 过)
In English:
“This is the first time I’ve come across this kind of thing.” (present perfect)
English needs to use the tense to show a new, present-relevant experience, not just a completed event or past memory.

I'm hesitatingnot sure whether toI will go to this studio or not in the future.

"Hesitating whether" isn't really used in English. You could say "I'm hesitating to return to that studio."

I planned to go to a new Pilates studio for a Pilates class today, but the class I had booked was cancelled and no one informed me.

TI'm tired of this kind ofsituations like things.

Fortunately, ithis is the first time I came across this kind of thing.'m experiencing this type of situation.