It's really hard for me. It's really hard for me.

You could also say "It's been really hard for me" since the thing that was hard for you is "I've been reading..." so the tenses match up better.

I find about 5 new words on each page. I find about 5 new words on each page.

I find about 5 new words on each page. I find about 5 new words on each page.

Spy x Family,: I'm up to page 42 Spy x Family: I'm up to page 42

Spy x Family, I'm up to; 42 page 42s in Spy x Family; 42 pages in

Neither your original title nor my correction is a complete sentence, but seeing "I'm up to" made it feel like it should be a complete sentence.

I've been reading English version Spy x Family lately and I'mve read up to pagthe 42nd page. I've been reading English version Spy x Family lately and I've read up to the 42nd page.

I would probably write it "Lately, I've been reading Spy x Family in English and am about 42 pages in."

I've been reading the English version of Spy x Family lately and I'm up to page 42 now. I've been reading the English version of Spy x Family lately and I'm up to page 42 now.

When you say "I've been <doing something> lately, and <result>", most native speakers say something like ", and now <result>" or "and <result> now." That's why I added "now" to the sentence. I feel it distinguishes the part that happened in the past, and your current status in the present.

I've been reading the English version of Spy x Family lately, and I'm up to page 42. I've been reading the English version of Spy x Family lately, and I'm up to page 42.

I've been reading the English version of Spy x Family lately, and I'm up to page 42. I've been reading the English version of Spy x Family lately, and I'm up to page 42.

I look up some interesting words, but not everything. I look up some interesting words, but not everything.

this is a good approach!

Sometimes, I'm happy and excited when I come across cool phrases. Sometimes, I'm happy and excited when I come across cool phrases.

Sometimes, I'm happy and excited when I happen to come across cool phrase. I'm happy and excited when I happen to come across cool phrase.

I don't think "sometimes" can be used this way because as an adverb, it can modify "happy" so it comes across to me as potentially reading like there are times when you come across cool phrases, but you don't feel happy or excited. Using "happy" and "excited" this way can come across a little childish. I'd probably say: "I really enjoy coming across new, cool phrases."

Sometimes, I'm happy and excited when I come across a cool phrase. Sometimes, I'm happy and excited when I come across a cool phrase.

Sometimes, I'm happy and excited when I come across a cool phrase. Sometimes, I'm happy and excited when I come across a cool phrase.

Sometimes, I'm happy and excited when I come across cool phrases. Sometimes I'm happy and excited when I come across cool phrases.

I don't think I would say this in my real life, but ait least, it would be bettercan't hurt to know. I don't think I would say this in real life, but it can't hurt to know.

I changed this a lot because it's hard to reconcile "but at least" and "it would be better to know" without writing a longer sentence to connect these better.

I don't think I would say this in my real life, but at least, it would be better to know it. I don't think I would say this in real life, but at least it would be better to know it.

"Some kinda"/"Some kind of" is actually really common, especially in everyday English.

I don't think I would say this in my realeveryday life, but at least, it would be better to know. I don't think I would say this in my everyday life, but at least, it would be better to know.

I don't think I would say this kin myd of thing in real life, but at least, it would be better's good to know. I don't think I would say this kind of thing in real life, but at least it's good to know.

I will be able to enjoy Spy x Family more, if I have lots ofa larger vocabulariesy. I will be able to enjoy Spy x Family more if I have a larger vocabulary.

Vocabularies isn't really a word in that sense, vocabulary is 語彙力.

I will be able to enjoy Spy x Family more, if when I have lots ofa larger vocabulariesy. I will be able to enjoy Spy x Family more when I have a larger vocabulary.

I will be able to enjoy Spy x Family more, if I have lots ofa bigger vocabulariesy. I will be able to enjoy Spy x Family more, if I have a bigger vocabulary.

You could also write this like "The more my vocabulary expands, the more I can enjoy Spy x Family."

I will be able to enjoy Spy x Family more, if I have lots ofimprove my volcabulariesy. I will be able to enjoy Spy x Family more, if I improve my volcabulary.

I will be able to enjoy Spy x Family more, if I have lots ofa bigger vocabularies.y in English. I will be able to enjoy Spy x Family more if I have a bigger vocabulary in English.