Hi, De_Fade
Firstly, yes VCE Chemistry can be quite a confusing subject. You're not alone in that. In fact, I felt quite the same when I started VCE Chemistry. So try not to get yourself too down; VCE Chemistry is a subject that requires some patience and persistence.
If you feel like your textbook is jumping ahead, perhaps you could simply try Googling some of the definitions/concepts you're unsure of. There's also some podcasts around that might be useful. Alternatively, you could purchase the A+ notes for Chemistry. These notes follow the study design really well, something which is unfortunately not always the case with textbooks, and the notes are really good at explaining concepts in simple terms and in logical orders, imo. The notes are also not particularly expensive.
If you find you're teacher to not be very good - somewhere we've all been at one point or another, am I right? - then perhaps you might consider a tutor, if you're serious about continuing with VCE Chemistry and doing well. A tutor isn't trying to satisfy an entire class and will be able to cater to your specific needs/questions/weaknesses.
Lastly, I'd recommend doing lots of practice questions. Start with textbook questions as these are usually the most straightforward, and then move onto more exam-style questions. See if your teacher has any practice papers he/she would be willing to give you. You'll find with VCE Chemistry that exam-style questions are quite varied in that they get you to apply basic textbook knowledge to a wide range of novel scenarios. Once you start doing lots of practice questions, similar topics will keep re-appearing and this'll help you consolidate your knowledge. Focus your study on completing questions that relate to topics you find most difficult.
Other than that, just keep at it! Many of the skills you learn in Unit 1 Chemistry are used in Units 2, 3 and 4 as well (e.g. the mole, intermolecular forces). You're only just learning these topics now and you'll have plenty more opportunities to get better at them.
Hope this is helpful!