I majored in German in college. Check out something called the High German Sound Shift. What it basically means is that some sounds from the original Germanic languages CHANGED in the transition to modern German. Also, there were some "sound shifts" in English.
For instance, the th sound that still exists in English changed to t/d in German. The d changed to t. English DeaTH = German ToD (rhymes with "goat" because final consonants in German are "voiceless"). OLD Germanic K often changed to CH in English: English CHurCH = German Kirche
Germanic ch (sounds like clearing your throat) became English gh: German laCHen = English lauGH. English niGHt = German NaCHt. English liGHt = German LiCHt. German feCHten = English fiGHt.
Once you know the correspondences you can easily "transform" an English word to German and vice versa--it makes learning vocabulary or guessing words MUCH easier.
Note that VOWELS *routinely* change in ALL languages. So there is no easy "replace THIS English vowel with THIS German vowel." Once you've done the CONSONANT "swap", you just have to try substituting vowels until you hit the right one: "Hmm ... English "light". Substitute ch for gh. German LiCHt. English "night". Substitute ... NiCHt. Nope, "nicht" means "nothing" in German. How about NOcht? Nope ... NEcht? Nope ... NUcht? Nope ... NAcht? -- Yup, English Night = German NAcht."