challenge vs achievement
Studying and making progress
Remembering and forgetting
Teaching and learning
hard work
100

a situation in which someone is trying very hard to win an argument or deal with a difficult situation

battle

100

decided to achieve something

set smb sights on

100

be easily remembered  

stick in my mind

100

to learn from a negative experience not to do something again

learn my lesson

100

to stay up late at night to work or study

burn the midnight oil

200

a difficulty or problem that prevents progress or success

obstacle

200

up to a satisfactory standard or quality

up to scratch

200

a bad memory 

a memory like a sieve

200

to show someone as a result of experience what not to do

teach him a lesson

200

to stay up all night, especially to study or work:

pull an all-nighter

300

something unusual, brave or entertaining that someone does

exploits

300

going to bed late and getting up early

burn the candle at both ends

300

are forgotten immediately

go in one ear and out the other

300

You are giving advice to someone about something they know more about than you

You're teaching your grandmother to suck eggs!

300

spend the maximum time studying

bury in books

400

something impressive and which often requires courage

feat

400

progressing rapidly

in leaps and bounds

400

helps me to remember / reminds me

jog smb's memory

400

It's difficult to make someone change their way of doing things, especially if they have been doing it for a long time.

You can't teach an old dog new tricks

400

to begin studying hard

Hit the books

500

an extremely unpleasant experience, especially one that lasts for a long time

ordeal

500

all the time

work round the clock

500

learn something to be able to repeat it exactly (even if you do not understand it)

learn by rote

500

study in a very concentrated way for a short time

cram for

500

to learn/know how to do a job or activity

Learn the ropes

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