I usually bring these things for my tripwhen I go abroad.

First, and the most important one, is my smart phone.

Unlike on my first trip, I can use maps, local guides even, and other informations are possible to use by on my phone.

After getting an USIM chip at the destination country, I can use all of them just like I am in my country.

You're technically correct because 'an' should be used before a word starting with a vowel. However, it sounds unnatural here. I can't really explain this - sometimes words that start with a vowel sound strange with 'an' and sound better with an 'a.' I think it's something that you will notice and pick up over time. Or maybe you will find a better explanation, haha. :)

The next thing I bring is some medicines.

I sometimes have an upset stomach sometimes, so I should take th, so I need to take medicines every time.

For other emergency situations like a headache and jet leg, I also take them.

I totally agree with this sentence, and I take lots of pictures during my travelings.

I usually bring these things for my trips abroad.

First and the most important oneforemost is my smart phone.

"First and foremost" is a set phrase.

Unlike my first trip without a smartphone, maps, local guides and even other informations are possible to use by can be found on my phone.

After getting an USIM chip at the destination country, I can use all of them just like I amit exactly as if I were in my own country.

Subjunctive II case

The next thing I bring is some medicines.

In the US, we don't use "medicines" for the plural form. We just use "medicine."

I haveget an upset stomach sometimes, so I should take the medicines every timbring it just in case.

For other emergency situations like headache and jet leg, I also take thembring those with me.

The last thing is my previouson the list is my old camera.

As you may know, the only picturestangible things which remain after trips are pictures.

I totally agree with this sentence, andiment so I take lots of pictures duringwhile I'm traveling.

With the pictures, I can remembercall my goofond memories at there.

Essential Things for When I Travel

I usually bring these things for my trips abroad.

FThe first and the most important onething is my smart phone.

Unlike with my first trip, maps, local guides, and even other kinds of travel informations are now possible to use byon my phone.

After getting an USIM chip at thein my destination country, I can useaccess all of them just like I amwould be able to in my home country.

The next thing I bring is some medicines.

Medicine can be used as plural and singular.

I have an upset stomach sometimes, so I should take the medicines every timeMy stomach can get upset, so I take medicine when this happens.

For other emergencyI also take medicine for other situations like headaches and jet leg, I also take themag.

Headaches and jet lag aren't usually considered emergency situations, but if they are for you, please feel free to ignore this.

The last thing is my previous camera.

Do you mean precious? If you do mean previous, "old" is a better choice.

As you may know, only pictures remain after trips.

I totally agree this sentence, andTherefore, I take lots of pictures during traveling.

With the pictures, I can remember mythe good memories at therefrom the places I've been.

When I travel abroad, I usually bring these things for my trip abroad.

Nothing is wrong with your sentence, but switching the clauses around sounds more natural in English.

FThe first and the most important oneitem is my smart phone.

Unlike my first trip,When I first started traveling, I had to use paper maps, and local guides even other informations are possible to use by; now, I am able to access all of this information using my phone.

I changed "Unlike my first trip" to "When I first started traveling". Using the phrase "Unlike my first trip" makes the reader think you are going to start talking about that trip specifically.

After getting an USIM chip at the destination country, I can use all of themmy phone just like I amwould in my country.

The next thing I bring is someitems I usually bring are a few types of medicines.

I haveSometimes I get an upset stomach sometimes, so I should take the medicines every time, so I make sure to have medication on hand.

"To have [something] on hand" is a phrase that means "To have something easily accessible or within easy reach".

For other emergency situations like headaches and jet leag, I can also take themose medicines.

The last thing is my previousimportant thing I bring is my old camera.

Added a few words for sentence clarity.
You could also say "the camera I used previously", as well.

I totally agree with this sentence, and I take lots of pictures duringwhile traveling.

With the pictures I save, I can remember my good memories at thereexperiences in the places I have traveled to.

I usually bring these things for my trips abroad.

First, and the most important one, is my smart phone.

Unlike mythe first trip, maps, local guides even otherime I traveled, with my phone I can see informations are possible to use by my phone.bout maps, local guides and even other things.

After getting an USIM chip at the destination country, I can uUse all of them just like I am in my country.my phone just like back home.

The next thing I bring is some medicines.

I have an upset stomach sometimes, so I should take the medicines every time.Sometimes my stomach gets upset, so I always make sure to bring medicine for it.

For other emergency situations like headache and jet leg, I also take them.bring medicine for that.

The last thing is my previousold camera.

As you may know, There is a saying “only pictures remain after trips.” and I totally agree and takes lots of pictures while I travel.

I totally agree this sentence, and I take lots of pictures during traveling.

With the pictures, I can remember my good memories at there.adventures traveling.