[Postcard] Incoming cards from Germany

Hello!
Today I'm received 2 cards from Germany (Official Postcrossing)
I'm never been to Germany before but i'm reading story from traveler and writer in Thailand.
[WANDER BOY หนทางยังเยาว์วัย : Thai language] He favorite's writer for me about travel.

I'm try to find style for post on my blog so please forgive me if you enter and see something strange.
I'm try with CSS and html but i'm think it not easy for me 😝

The first one send from Sanne2506 it used 21 days (i'm think it slow because post in Thailand)
Here the front of postcard - MANNHEIM

Just i said i'm don't know about anything with this city.

but it look like important when i'm search information about this city.

(I'm want my country keep information about local or town like this but...just i know it collect on paper and keep it on old building so i'm never know about local city in Thailand too)

This is 2 stamp she sent to me
first - Kieselalge Mikrowelten (Dilute the algae) (0.70 DEM)
i don't know what it it (again!) so i'm try translate with google but when result show i'm don't know what is it ? because translate from Germany to English and to Thai it don't help me.

two - Blüte odermennig (Flower ormany) (0.70 DEM)
I'm guess it about flower structure or something like that ?

The second card sent from oktober12 it used 10 days to Thailand.
This is front of postcard

'Aachen' is important town i'm guess
(i'm see information on Wikipedia and it so long... i'm summarize with my self)

And this is stamp he sent to me
'100 jahre möhnetalsperre' (0.90 DEM)
(it look like Reservoir or dam)