The graph shows Underground Station passenger numbers in London

The linear graph demonstrates the number of passengers that attendsutilise the London Underground Stations between 6:00 a.m. and 22:00 p.m. in London.

At 6:00 a.m. the number of people using theassengers at station is 100, which doubles by 7:00 a.m. , before reaching a peak of 400 passengers inat 8:00 a.m. Furthermore, for a subsequent 2 hours the number of passengers experiences significantly drops to just under 200 passengers.

In this correction I am being very picky, but this would be a more natural yet still professional way to word things.

In afternoon the number of visitors go uppassengers rises slightly despite a large decline over a period between 15:00 and 16:00. When we focus on evening sessions ,hours it is noticeable , that this period of time follows a similar patterns as we cwould observe forin the morning .

So far you have swapped between saying “passengers” “visitors” and “people”. It is good to keep this consistent. As we’re talking about transport it would be good to stick to “passengers”

Then the figure oscillthen stagnates at around 150 passengers until closing time.

I know what you are saying, but “oscillates” doesn’t fit well in this context.

Overall, it is important to mention, that during the peak hours (of 8:00 and 18:00), the numbers of passengers is four times greater than at 6:00 and 16:00, respectively,when Underground Station iss are visited by the lowest number of passengers(exactly 100).

The graph shows Underground Station passenger numbers in London

The linear graph demonstrates the number of passengers that attendsvisit Underground Station between 6:00 a.m. and 22:00 p.m. in London.

At 6:00 a.m. the number of people using the station is 100, which doubles by 7:00 a.m. , before reaching a peak of 400 passengers inat 8:00 a.m. Furthermore, for the subsequent 2two hours the number of passengers experiences a significant drop to just under 200 passengers.

We typically spell out numbers smaller than 10.

In the afternoon, the number of visitors goes up slightly despite a large decline over a period between 15:00 and 16:00. When we focus on evening sessions , it is noticeable , that this period of time follows similar patterns ato the ones we could observe forin the morning .

You could also say “to the ones we observed in the morning.”

Overall, it is important to mention, that during the peak hours ( 8:00 and 18:00), the numbers of passengers is four times greater than at 6:00 and 16:00, respectively, when Underground Station is visited by the lowest number of passengers (exactly 100)

The way that “respectively” is used in this sentence confuses me a little. If the number of passengers at 8:00 and 18:00 are unequal, the number of passengers at 8:00 is four times the number of passengers at 6:00, and the number of passengers at 18:00 is four times the number of passengers at 16:00, then this usage makes sense.

However, the last part of the sentence implies that Underground Station is visited by exactly 100 passengers at both 6:00 and 16:00, which would mean that there are exactly 400 visitors at both 8:00 and 18:00 and there is no need to differentiate the order of the quantities.

In my opinion, a better way to use “respectively” would be to say:
“Overall, it is important to mention that during the peak hours (8:00 and 18:00), the number of passengers is four times greater than at 6:00 and 16:00, when Underground Station is visited by the lowest number of passengers (100 and 84, respectively).”

This would imply:
100 visitors at 6:00
400 visitors at 8:00
84 visitors at 16:00
336 visitors at 18:00

If the number of visitors at 8:00 and 18:00 are the same, and the number of visitors at 6:00 and 16:00 are the same, I would omit the “respectively” to improve the sentence flow.

I hope this comment helped- let me know if you have any questions!