Here’s a refined version of your text with improved clarity and natural flow: Over recent decades, trends in leisure activities among the elderly in Europe have changed significantly. The number of people participating in activities like hiking and internet surfing has steadily increased, with hiking becoming the most popular activity, reaching 80% participation. While internet surfing was understandably uncommon before the 2000s, it rose to 50% participation in the 2010s. In contrast, activities like reading, theater, and sports did not show a consistent upward trend during this period; their popularity fluctuated over time. For instance, theater, which was enjoyed by 50% of people in the 1980s, declined in the 1990s but gradually regained its former popularity. Overall, all of these activities, except theater, saw higher participation rates in the 2010s compared to the 1980s.

This is how I would say/write your response as a native: During the last few decades, trends for leisure activities for elderly people in Europe have changed significantly. The number of elderly people partaking in leisure activities - such as hiking or going on the internet - have increased through the years, making hiking the most popular activity for elderly people, with roughly 80% of the demographic participating in it. While going on the internet, for obvious reasons, was not a popular activity before the 2000s, it has since grown to entertain over 50% of the elderly population. On the other hand, activities such as reading, theatre, and playing sports have not had a constant increase in participation during the same period. As a matter of fact, theatre - which during the 80s was chosen activity by the 50% of the people - started becoming less popular around the 90s. However, trends are showing that it is rising in popularity again. (I can't make sense of the last sentence). As Simon said, it's not technically wrong and you would get your point across to a native speaker it's just not natural sounding. From my understanding, IELTS is a test you might have to take before going to an American college - specifically graduate school. If you plan to go to school, a paper written like this may get points deducted for grammatical structure although professors may go easy on non-native speakers. I don't mean to nit-pick but I want the best for you and I hope this helps!

Hi Martina. Well done. A nice piece of IELTS writing. A few suggestions from me, and I’m sure other of your colleagues here will have more too.. It doesn’t sound quite natural (though not wrong) to say ‘reaching the 80% of people doing it’. I’d say ‘with 80% of people doing it/taking part’ or ‘reaching 80% of the population’ theatre which (rather than that) but is slowly coming back

You need to post the question. Also, post your writing in “exercises” not “questions”.