Jól írtam ezeket a mondatokat (angol)?

Szövegkörnyezetttől függ, de valószínűleg I had never been, ha később már voltál.

... a lot of useful information about how ...

some guyS

without paying and started to make A noise

when we had the opportunity to try to copy some famous painters' works (már ha több festő volt) Itt van a work-nek többes száma.

A feltételes mondatban ugyebár nem csupa would van, ráadásul az elejét kettes conditional-nek vetted, a vége meg értelemszerűen hármas: lett volna. Szóval kettesben az if után múlt idő kéne, hogy legyen (lasted és were), de most neked nem az kell, hanem hármas: ... had lasted longer and the security guards had been stronger (vagy a biztonságra gondolsz? Mert az meg safety), this festival would have been more interesting. (Bár nem logikus, hogy a biztonságnak mi az összefüggése az érdekességgel. Inkább azt írnám, hogy would have been more fun.)

I HAD never been AT an open-air exhibition before, because UNTIL THAT I HAD always thought that they were boring and SO I would just waste my time.

During the festival, we were able to learn useful facts like how we CAN safe our planet.

In the second evening some guy got in without payING for it and started to make noise.

The highlight of the festival was when we HAD THE OPPORTUNITY TO COPY famous painter's workS.

If this occasion would HAVE lastED longer and THE security WERE SOMEWHAT TIGHTER this festival could HAVE BEEN more interesting.