I love summer because my tensionergy is so high.

Tension is similar to stress. Energy seems to fit your meaning better.

Summer has a lot of events or someand activities.

Music festivals take place during this season.

I love EDM (electronic dance music), so I am looking forward to going to the festival every year.

"I am looking forward..." is the present progressive tense, which would usually be correct for a continuing action. But in this case, people say "I am looking forward to..." about an individual event. They say "I look forward to it every year" about annual events in general.

Last summer, some famous musicians came to Osaka, so I went too.

It was the greatest time of my life.

However, most of music events were canceled due to coronavirus.

I was so shocked to hear that, however I cannot do anymore than to hope endingfor coronavirus to end.

I love summer because my tension is so high.

"tension" has mostly negative meanings like anxiety or nervousness. Try a different word like "excitement" or "enthusiasm". Or better, use an adjective like "exciting" ("I love summer because it's so exciting"), or a verb ("I love summer because it excites me so much"). When referring to emotions, we don't say things like "my ___ is so high", it sounds awkward.

Summer has a lot of events or someand activities.

Music festivals often take place during this season.

I love EDM (electronic dance music), so I am looking forward to going to the festivals every year.

"I am looking forward" and "the festival" suggest a specific event, these changes make the statement more general.

Last summer, some famous musicians came to Osaka, so I went to see them.

It was the greatest time of my life.

Alternatively, if it was not the best time of your life but still great: "I had a great time."

However, most of the music events were canceled this year due to coronavirus.

I was so shocked to hear that, however, I cannot do any more than to hope endingthat coronavirus ends.

"cannot" is very formal, and the word is not used in casual speech/writing. It isn't wrong, but "can't" would be more natural.