Ok, I'm not going to sugar-coat things: the jump from GCSE to AS level in languages you're not native fluent in is massive. With a good grasp of languages, a willingness to work and a desire to understand grammar/literature and develop speaking skills, however, it is entirely possible to overcome.
For example, in my case, I had minimal Spanish teaching prior to AS - I could form sentences like you and my basic grammar was strong but I was by no means an essayist or conversationalist. My final AS grade, however, was around 18 marks off of full UMS in Spanish.
There are a couple of key areas to work on, all building up to A2:
- Grammar, including tense conjugation, agreement, vocabulary and translation
- Speaking in a debate setting which requires research into your topic and familiarity with speaking Spanish
- Reading (reading comprehension, multiple choice questions), writing (essays on a theme*), listening (understanding listening, condensing information)
- *Within writing there is also literature where you research a particular book/movie and write an extended essay on this book/movie on a theme
The good thing is that all of these can be practised! For grammar you can quiz yourself using SpanishDict, Duolingo or flashcards - I recommend Palabra por Palabra and the Hodder (ironic title) education books. Make vocab lists on the key themes (youth culture, environment, world around you, education, health) and memorise/quiz yourself on these either writing them down or using Memrise. Translation is also an important skill which builds on all the above so past papers will be useful here as consolidation.
Speaking is practice and research. The more you speak in Spanish on that theme, the better. Research does not have to be intense, it can just be straightforward say if you like climate change what are the key issues, some statistics etc. Reading, writing and listening are all based on practice so listen to podcasts in Spanish, read articles and newspapers and do the sample papers online.
Literature is where it is not just practice-based. There you have to demonstrate your understanding of the text so you have to get to know it very well by reading it thoroughly, making notes and writing essay plans for key questions. It is also very important to read the question multiple times and to make sure you are answering the specific question (also true of the discursive/creative essay). But, as with all the other components, the more you practice the better you get!
This is probably more than you need but it should help you to make a decision. If you're put off by this then maybe a language isn't the right choice but if you are willing to put in the work it is very rewarding (and the progress is really obvious unlike some subjects)!
What other subjects are you choosing to do?