How long would it take you to learn/memorise french vocabulary? Watch
If you have a hard time to memorize, follow a step-by-step method: give yourself reachable goals. Start by memorizing a few words. Quiz yourself a few times a day. It does not need to be long and you can do that while waiting at the doctor's, in a bus, walking on the street... If you can remember the words, add two more, and quiz yourself from the beginning... It is better to learn less and know perfectly the spelling, than trying to memorize everything and retaining little.
Repetition, repetition, repetition... If you stop practicing, your short term memory will erase the information. The memorization process has three steps: short-term memory (such as "my doctor's appointment is Monday at 2pm, once you went there, the info is erased to make room for new content), long-term memory, muscle memory (when you can use and master the material).
Bon courage !