Native English speaker here. Learned Latin (up to Latin VI), Spanish (to III), French (to II), and ASL (to II) in middle school and high school. While I understand the sentiments of acm2010, it is ultimately impossible not to relate a new language back to one’s native language (unless you are under the age of 12).
The simplest way to pick up Japanese is to first reinforce your language concepts. A lot of people, no matter what language they speak, tend to USE grammar points without actually remembering them (for example, transitive/intransitive words). Vocabulary, especially kana, will just be raw rote learning for a while. Japanese, unlike English, has a very nice stacking component due to its pictographic nature, so it will get easier as you go along.
My recommendation for working out the differences outside of your class is to find parallels within grammar points. A generic example would be transitive/intransitive verbs. Japanese verbs usually use the same kanji for verbs while changing the hiragana ending in order to conjugate (similar to English and Spanish). Two examples of these pairs that are quite common in everyday Japanese are kaesu/kaeru and hajimeru/hajimaru. Transitive/intransitive verb pairs will often follow this policy: Transitive verbs ending in -su will change to -ru (intransitive) and transitive verbs ending in -eru will change to -aru (intransitive). Putting this into kana, you would see 返す・返る and 始める・始まる.
While Japanese requires a large amount of memorization in order to gain vocabulary, its grammar points are very persistent with few irregulars. Differentiating -ru conjugation verbs with -u conjugation verbs ending in -ru can be confusing, but once you can see the difference, you will always know how they conjugate.
While it seems like a very different language, the consistency that (textbook) Japanese has makes it very easy to related to English when comparing by grammar rules. Yes, a ton of those rules are different between the two languages, but, if you directly compare and memorize how those specific systems work, you’ll find yourself understanding the language much faster.
The biggest hurdle you’ll probably encounter regarding both word usage and grammar is the contrasting natures of the purpose of words between the languages. English is a fairly objective, detail-oriented language. It’s not an eloquent, poetic language by nature, especially when spoken normally. Japanese, however, is very subjective and concept oriented. The same idea can be spoken many different ways depending on the speaker, the person receiving the speech, the circumstances in which the words are being spoken, and how the words being spoken relate to both individuals. Unfortunately, it’s very difficult to learn those concepts in a classroom, or any situation where regular exposure to natives isn’t present.
As konekush said, keep an open mind. JapanExchange and (lesser so) WaniKani forums have both questions and answers for almost anything you need to know, and taking the extra time to research any small things that come to mind will add miles to your progress in the language. If you have a question or thought, no matter how small, look it up! Language uses many different parts of our brain, so even the smallest realization can lead to a chain reaction of understanding.
One of the biggest caveats I can mention to NOT do when relating English to Japanese. DO NOT RELY ON ROMAJI. Learning hiragana/katakana is probably the most important first task. Since you’re on WaniKani, it’s safe to assume you’ve already at least started that process. You’ll learn fairly quickly into your kanji studies that Japanese is filled to the brim with homonyms due to its implementation of Chinese without tonal inflection. If you rely on spelling of words in romaji (especially with the differences in romaji schools [Example: Kyōtō vs Kyoutou vs Kohtoh vs Kyootoo]), you’ll have a lot of trouble attempting to type in Japanese and differentiating verbs (Example: Tsukeru - 付ける: to attach、点ける: to turn on、漬ける: to soak、就ける: to appoint). It would be bad if you told someone you wanted to soak a public official or to soak your cell phone!