My favorite piece of clothing is a long black party dress with a chiffon skirt and a rhinestone bodice.
(My favorite outfit is a long black party dress that includes a chiffon skirt and a rhinestone bodice.)

I bought it at a store specializing in party dresses and I used it for the first time at my brother's wedding.
(I bought it at a store that specializes in party dresses, and I wore it for the first time to my brother's wedding.)

From that moment I have used it on many occasions and special events.
(Since then, I have worn it on many occasions and for special events.)

One day at a party I met a girl who was wearing the same dress as me. It was very funny. We took a picture together and since then we are friends.
(One day, at a party, I met a girl who was wearing the same dress as me. It was quite funny. We took a picture together, and since then we have become friends.)

Hello, It´s been a while
(Hello. It's been a while.)

Well, I don't know what to tell you, I think my english grammar have started go down (I'm not sure about this expression).
(Well, I think my English grammar has begun to decline.)
This month I will celebrate my birthday, I'm old hahahha. I'm studying again, I study Tourism so I need to learn english quickly.
(This month I celebrate my birthday- I'm old. Ha. Ha. Ha. I'm studying again. I'm studying tourism, so I need to learn English quickly, but I'm lazy these days.)
But I'm lazy in these days. Maybe it is because the days has been hot and that is too much for me.
(Maybe it's because it has been so hot lately, and it's all just too much for me to deal with.)

To sum something up means to summarize it or share only the very important details. For instance, if you borrow your friend's car and then wreck it in an accident, you don't go into all of the details of what happened that led up to the wreck. Instead, you start by simply stating that the car was wrecked in an accident. Your friend will ask questions to get the additional details that they believe are necessary. Communicating this way tends to be more effective.

Well, I have enough experience working with video and audio that I am confident I can offer you some insight into this confusion you have. I lived near and worked in Hollywood for a time. When you are watching a professionally produced movie, the audio and the video were recorded separately. In post-production, the time period when all the editing takes place, the audio track is matched up to the video track. When movies are also dubbed in other languages, they simply replace the original audio track with the new audio track for the alternate language. Since the way the mouth moves is different for different languages, they cannot align the new audio track with mouth movement in the video track. Instead, they break down the scenes of the movie into smaller moments and try to match the general pace of the audio to those moments (known as beats). These new audio tracks are recorded by voice actors in recording studios, who use a script specially prepared in their language and the muted video footage (no audio). This allows the voice actors to match the pacing and vocal dynamics to the video as best they can using their own language.