Is that ok go alone? Reservation is necessary, too? (at lunch time)

Yes. You can sit at the bar. I made reservations literally 10 minutes ahead of time.

I think you can go alone. I think you should make a reservation.

you can go alone but I recommend to make a reservation.

Definitely. No problem at all. I didn't made any reservation at all.

Definitely ok to go alone and I usually make last minute reservations.