Breakdown of Estou feliz, mas logo que tiver a pulseira, entrarei no festival.
mas
but
ter
to have
estar
to be (temporary / location)
em
in / on / at
Questions & Answers about Estou feliz, mas logo que tiver a pulseira, entrarei no festival.
Why do we use tiver instead of tenho after logo que?
Logo que means 'as soon as'. When it introduces an action that hasn't happened yet, it triggers the Future Subjunctive tense. Tiver is the Future Subjunctive form of ter (to have).
Why do we say entrarei no festival instead of just entrarei o festival?
Could I use Sou feliz instead of Estou feliz at the beginning of this sentence?
Using Sou feliz would mean 'I am a happy person' in general. Estou feliz means 'I am happy right now'. Because this sentence is about the excitement of a specific moment before a festival, the temporary state of estou fits much better.
Is entrarei the only way to say 'I will enter'?
While entrarei is the correct Future Indicative form, it sounds a bit formal. In everyday spoken Portuguese, you will very often hear people use vou (I go) plus the infinitive, like vou entrar no festival. Both are perfectly fine to use here.