No worries! If we consider the fact that you don't enjoy any subject, you should probably use reverse psychology to address this issue, i.e. instead of thinking about which subject you like/enjoy (which obviously is not something that applies to your particular case), thinking about which subject you are least likely to find unenjoyable would be a good approach to decide which subject to take. To help you further, let's explore what Japanese Continuers and Economics can help you do beyond the HSC:
Japanese Continuers:
As we all know, learning a language may potentially make a number of opportunities available to you, whether it be in Australia or overseas. For example, learning a language may open the door to a career in teaching, such as becoming a Japanese teacher for example. In addition, you can take your linguistic skills beyond the HSC, and study a Bachelor of Arts and specialise in Interpreting and Translation, where you can further develop your Japanese language skills and eventually become a translator/interpreter.
Economics:
What does Economics entail? Preliminary Economics covers concepts such as consumers, markets (including labour and financial markets) as well as the government. HSC Economics expands on those concepts by introducing you to the global economy, Australia's place in the global economy, economic issues as well as economic policies and management. There is quite a bit of writing in Economics, particularly when considering Section III and Section IV essays, meaning there is also quite a bit of content to be covered. If you take Economics, you need to make sure you are regularly studying and staying up to date with the content, and seeking assistance with any concepts/aspects of the subject that you feel you are struggling with.
Studying Economics allows you to gain foundational knowledge relevant to the field of economics, one of the many areas of business. You can take this knowledge beyond the HSC and study a degree such as a Bachelor of Business/Commerce with an Economics major, a Bachelor of Economics and (potentially) a Bachelor of Actuarial Studies. With such degrees, you could be looking at career opportunities such as economist, actuary and (possibly) accountant.
If you feel you'd like to take English Extension 1 for year 11, you should consider your performance in English throughout year 10, i.e. whether you have been performing consistently well. If that is the case, then English Extension 1 may indeed be a good subject to take.
Whether or not you'll be doing Mathematics Extension 2 in year 12 is something that is determined by your year 11 results in Mathematics Advanced and Mathematics Extension 1, so it's probably not a good idea to think about Mathematics Extension 2 this early, particularly when you seem certain that you want to take Mathematics Extension 1.
Whether or not you will end up dropping a science is also something that will be determined by your year 11 results as well as your own opinion in terms of whether you feel you have enjoyed that particular subject, meaning it's not useful to speculate this early.
Some additional subjects you may wish to consider are Business Studies and Information Processes and Technology (IPT). Although they are not considered to be the best in terms of enjoyment (some students describe Business Studies as "dry"), the content taught in those 2 subjects is relatively easy to learn and understand, meaning you are likely to achieve great marks in either of those 2 subjects, provided you are regularly studying and staying up to date with the content, allowing you to perform well in assessment tasks/exams.
All the best!