Since you are asking for some RC advice, here is some general advice:

To improve in single-paragraph passages, you first need to master the individual topics: Strengthen the Argument, Weaken the Argument, Resolve the Paradox, etc. As you learn about each question type, do focused practice so you can track your skill in answering each type. If, for example, you get a weakening question wrong, ask yourself why. Did you make a careless mistake? Did you not recognize the specific question type? Were you doing too much analysis in your head? Did you skip over a keyword in an answer choice? You must thoroughly analyze your mistakes and seek to turn weaknesses into strengths by focusing on the question types you dread seeing and the questions you take a long time to answer correctly.

Another major mistake that people make when training for single-paragraph passages is that they do practice questions too fast. To get single-paragraph passages questions correct, you have to see exactly what is going on in the passages and answer choices, and you likely won't learn to do so by spending a few minutes on each question. At this stage of your training, you may need to spend even fifteen minutes on each question, learning to see what there is to see. Here is a way to look at this process. If you get a new job in a field in which you are not experienced, you may not be as fast as the other people working with you, but you know you have a job to do and you make sure you learn all the angles, so that you do the job well, if not as quickly as those around you, Rushing through the job and doing it incorrectly would not make sense. Then, as you gain more experience, you learn to do the same job more quickly. Think of single-paragraph passages questions similarly. Your job is to do what? To get through questions quickly? Not really. Your job is to get correct answers.

So, first you have to learn to get correct answers, generally at least 10 to 15 in a row consistently, and more in a row would be better. That is your job, and if it takes you fifteen minutes per question to get correct answers consistently, then so be it. Only after you have learned to get correct answers consistently can you work on speeding up. Working quickly but not doing your job is useless. Better to work slowly and learn to do your job well. You can be sure that with experience, you will learn to speed up, and then you will still be doing your job well, i.e., getting correct answers consistently.

Finally, a key aspect of getting correct answers to single-paragraph passages questions is noticing the key differences between trap choices and correct answers. Trap choices can sound temptingly correct but don't get the job done. The logic of what a trap choice says simply doesn't fit what the question is asking you to find. So, to get better at your job, learn to see the key differences between trap choices and correct answers.

To improve in multi-paragraph passages, you need to focus on understanding what you are reading. When you are incorrectly answering multi-paragraph questions, it’s partly because you do not truly understand what you have just read, right? Thus, you likely have to slow down in order to (eventually) speed up. At this point, your best bet is to focus on getting the correct answers to questions, taking as much time as you need to see key details and understand the logic of what you are reading. You have to learn to comprehend what you read, keep it all straight, and use what you are reading to arrive at correct answers. If you don't understand something, go back and read it one sentence at a time, even one word at a time, not moving on until you understand what you have just read. There is no way around this work. Your goal should be to take all the time you need to understand exactly what is being said and arrive at the correct answer. If you can learn to get answers taking your time, you can learn to speed up. Answering questions is like any task: The more times you do it carefully and successfully, the faster you become at doing it carefully and successfully.

Another component of understanding what you are reading is being “present” when reading. Don’t worry about how things are going at work, or what you will eat for dinner, or even how long you are taking to read through the passage. Just focus on what is in front of you, word by word, line by line. Furthermore, try to make reading fun. For example, even if you are reading about a topic that bores you, pretend that you are the person making the argument. By doing so, you will make the passage more relatable to YOU, and ultimately you should be able to read with greater focus.

One final component that may be tripping you up is that, as with single-paragraph passages, multi-paragraph questions contain one or more trap answers that seem to answer the question but don't really. So, once again, you have to learn to see how trap answers seem to follow from what the passages say, but don't really, while correct answers fit what the passages say exactly.

Feel free to reach out with further questions.