Errors:  

Double "the" before United Kingdom.

Corrected version:

In the first decade, the United Kingdom and Sweden led the graph of CO2 emissions per person, around 11 metric tonnes, while Italy and Portugal had below-average emissions.

Improved version:

During the initial decade, the United Kingdom and Sweden prominently led the graph of CO2 emissions per capita, with approximately 11 metric tonnes, while Italy and Portugal exhibited emissions below the average.

Errors:  

incorrect verb form ("goes" should be "went") 

missing article ("coma" should be "comma")

missing articles ("sudden increase" should be "a sudden increase" and "2007 year" should be "2007")

Corrected version:

In the last decade, the UK and Sweden experienced wild fluctuations and decreased to approximately 8 or 7.5 metric tonnes, while Italy and Portugal saw a sudden increase in average CO2 emissions, leading the graph in 2007.

Improved version:

During the final decade, the UK and Sweden encountered significant fluctuations, resulting in a decrease to approximately 8 or 7.5 metric tonnes. Meanwhile, Italy and Portugal experienced a sudden surge in average CO2 emissions, dominating the graph in 2007.

Errors:  

redundant "of" ("year of 2007" should be "2007")

incorrect verb form ("decrease" should be "decreased")

missing article ("the table" should be "a table")

Corrected version:

In 2007, the most fluctuating year in terms of CO2 emissions, the UK and Sweden decreased significantly, while Italy and Portugal surged ahead and topped the table.

Improved version:

The year 2007 witnessed the most dramatic fluctuations in CO2 emissions. While the UK and Sweden experienced substantial decreases, Italy and Portugal surged ahead, securing the top position.

Errors:  

- Misspelled word ("sutely" should be "subtly").

Corrected version:

Initially observed is a subtly decreasing trend for both the United Kingdom and Sweden.

Improved version:

Initially, a subtle downward trend is evident for both the United Kingdom and Sweden.

Errors:  

missing articles ("the last decade" should be "the last decade of CO2 emissions" and "the other two" should be "the remaining two").

Corrected version:

In the last decade of CO2 emissions, two countries will experience a sudden decrease, while the remaining two will increase. That year reflects the actual impact of CO2 emissions per person from 1967 to 2007 for each individual country.

Improved version:

During the final decade of CO2 emissions, two countries will witness a sudden decline, while the other two will see an increase. This year provides a genuine assessment of per capita CO2 emissions from 1967 to 2007 across individual nations.