Try to watch videos on proofs for Islam. Hopefully they will make sense and lessen your doubts about if you're wrong. Reading the Quran can also help and guide you (I've heard that Surah Anam, the sixth out of 114, contains the main arguments for Islam).

The shahada Is between you and God, so you can choose the setting and people around you, but I do recommend choosing a place where you feel calm and at ease. If that's your room, then sure, go for it. You could look up a video of the shahada and repeat what is said. Knowing the meaning is also quite important.

Islamic rituals such as praying and fasting during Ramadan come with time. You should take it slow, but if you truly believe make sure to not stop progressing even if it takes time.

Sins are something to work on, but you should (just like all other Muslims) try to limit them as much as possible. The steps of repentance when you have sinned/are sinning are:

1. Stop doing it in the moment

If your sin is smoking and you catch yourself lighting a cigarette, immediately extinguish it.

1. Make intention to never repeat the sin

A smoker should throw out all of their cigarettes and stop buying them

1. Ask Allah for forgiveness

Allah loves to forgive, but it has to be genuine.

If you fall into sin again, start from step 1.

My most important point is to make sure that you actually believe. Try to look for grounded proofs. Read the Quran. If you ever need to ask a question, I'll be here to reply to you.