You improve reading speed by reading more regularly, stopping the habit of saying words in your head, and using your eyes to scan in chunks, while comprehension improves when you read actively with a purpose. Speed and understanding grow together with practice; you do not have to trade one for the other.
Read more, every day. Like any skill, reading gets faster with regular practice. Even 15 to 20 minutes of daily reading, of anything you enjoy, steadily builds your speed and vocabulary.
Stop sub-vocalising. Many slow readers silently say every word in their head, which limits speed to talking pace. Practise taking in groups of words at a glance instead of one word at a time.
Use a guide. Running your finger or a pen under the line keeps your eyes moving forward and reduces re-reading the same line, a simple trick that noticeably speeds you up.
Read actively for comprehension. Before reading, ask what you want to learn. While reading, look for the main idea of each paragraph. After, summarise it in a line. Active reading makes you understand and remember far more.
Example: A Class 11 student in Chandigarh with a heavy syllabus practised reading with a pen as a guide and summarising each section in one line. He got through chapters faster and actually remembered more.
One practical tip: After reading a page or section, look away and recall the main points before moving on. This single habit boosts both comprehension and memory, and stops the common trap of reading without absorbing anything.