Keep talking to your grandma, and you will get plenty of encyclopedia entries before even meeting any other characters.
Check entries out by pressing 'Esc' button in-game and choosing 'Encyclopedia'.

You will inevitably stumble across this one, escpecially when interviewing Matyas. The game itself will show you how to repeat a conversation when you ran out of questions but didnt get all the answers yet.

Simply speak to everyone.

Complete the game by making your granddad and Egon meet each other.

The 1st minigame unlocked during the conversation with grandma.
Hide those leaflets behind the loose ceiling tile, which is right above the center of the room.

The 2nd minigame unlocked during the conversation with grandma.
"No, my wife is in the bedroom, wait until she gets dressed."

The 3rd minigame unlocked during the conversation with grandma.
Start from the back of each room and finish with objects at front. Otherwise the closest ones would start overlapping the farthest ones, and you wont be able to finish the challenge.


The first minigame unlocked during the conversation with Matyas.
You have to go for this route to unlock Matyas' minigames:
>> What was the occupation for you? - I'm not interested in the uprising. - I'm interested in what you did in the resistance. <<
The actual solution for Old Philatelist:
"Just an empty thermos and envelopes I collect for stamps."

The second minigame unlocked during the conversation with Matyas.
(How to unlock Matyas minigames, see above at 'Old Philatelist' section.)
The actual solution:
1. Wait until soldiers change their position a few times and disappear. Approach your target then.
2. Wait. You might or might not buy a newspaper at some point when asked. Don't help an old woman. Hit your target right after the old lady disappears, at the very end of your time resource.
3. You can approach your target at any point, they will tell you to wait in any case. Upon asked to hand over the leaflets, refuse.

The first minigame unlocked during the conversation with Josef.
The easiest minigame achievement by far. You dont even have to care if objects are truly safe or unsafe, simply destroy all of them.

Unlocked during the conversation with Marie.
You have to go northeast direction. Eventually approaching a ranger station, steal some clothes. Then move northwest. At the train station, tell either the conductor or a young woman you were robbed and need to get to Prague.

Unlocked during the conversation with Egon.

Unlocked during the Secret Admirer route (see Hard To Get section), which is complicated, but the mingame itself is an easy job.

You will get this one for obtaining 2 coins in all minigames during one and the same playthrough.

This achievement suggests you to find all information for each character. No secrets there, just tedious repeat. You have to investigate all the routes in conversations, including ones where people slam their door in front on you.
There still might be one piece of information missing from your grandma's information row, which is fine, you'd still get The Whole Story achievement as long as you rummage through all other eventually unlockable characters.

For this achievement, you must complete both all characters conversations routes (see above) and Secret Admirer route (see below).

A kind user Gingergal was the one who initially discovered the proper route and shared it.

At any point, go speak to Josef and choose those lines [you might simply skip minigames if you want]:
- what did you do after the assassination?
- you were a journalist under the Protectorate
- did you write about assassination?
- who were?
- werent you collaborating?
- lets change the topic
- what did the gestapo ask you?
- you know nothing about grandpa's arrest?

After that, a new option unlocks in Grandma's conversation. You have to get it at the first try, so there is no room for wrong answers. Follow the proper route precisely:
- did you know some German man? [2nd response]
- what did you do in city hall? [1st answer]
[After this one you unlock the poetry minigame and might get Pen is Mightier than the Sword achievement if you choose the topmost answer every time.]
- and what did you say after the poetry [2nd response]
- and then? [1st response]
- I would like to read that [1st response]

When deciphering grandad's diary, this is what you are aiming at.
Note: a key to the puzzle changes with every walkthrough.
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The second 'write an article' minigame unlocked during the conversation with Josef; you dont acquire any specific achievement for this one, but you'd still have to get 2 coins for it.
Simply choose the topmost option at all times. They have to be praising the current regime, berate Britain and attempt to scare local populace.