Hello, unknowns!
First of all, sorry for posting in English, but I do not know any English 
--my girlfriend does, but just a little bit which is not enough ...--
I have been working in the past months:
It's called BoardGameMarket, and it's an Android app for helping you discover, buy and sell your board games.
You can upload your games to the app, search for the games you are interested in, chat directly to the sellers and meet them to make the transaction in person.
LINK: Play Store
The app now has the following features:
- Register and user profiles (nickname, profile pics)
- Real-time chat, with emoji support
- push notifications
- Game form with category, description, price, up to 6 pics and extras (exchange, shipping, etc)
- Basic search filters (by text, category, price, distance ...)
- Favorite games list
- Mark games as reserved and sold
- User ratings after transaction has been made
- Translated to 5 languages (including English and German)
The idea is to keep developing new features and correcting errors.
Of course, any idea or suggestion is more than welcome, just email us: info@boardgamemarkt.com
For Apple users, an iOS version is being developed but it's not ready yet... we'll keep you posted.
[Blockierte Grafik: https://thumb.ibb.co/hAYsew/8d9x_Cb_RFa_Ib_PTr8_Oe_J2k_Laaz_MJnzx_I3p_Gu3ar8y_WIt6w_I_9_FV6_XV7r_FF0v_Sjuz9_K2_XA_h900_rw.png] [Blockierte Grafik: https://thumb.ibb.co/eEr0XG/g_CO1_A48_HAWEQGbp_Hmv_Ic_OWvmyhnet_Qm_Dj_I4_Pid_IXK4_K5ru_Df_Fk_Zdn_C8_M5u3glfanr_Y_h900_rw_1.png] [Blockierte Grafik: https://thumb.ibb.co/h1DfXG/w_TGrum_DBQzh_IVg3b_Cxn_Av_Xmvt_Dmh7_DAf_W_h9_OP2o_Df_Cte_K9_LC554_Dve_Ldzv_Osxe_Sdxm_h900_rw_1.png] [Blockierte Grafik: https://thumb.ibb.co/nR3Qzw/x_It8_TYiva_YHWx7_WF4_SEu7_Xw_AKq_UVWn_YB_6_FS4a3e3i_V8_IZap2_C7k4w7g_BC_Kafq_QWm_B_h900_rw_1.png]
Links:
Please, keep in mind the app is just starting (I released it officially on Dec 20th) so it needs contents to be more attractive...
For now, we have a growing community in Spain (where I live) but we expect to have more international friends!
That's why I encourage you all to upload your games: it's free and you'll be helping another board game community to grow 
Also, you can help with just sharing links and recommendations.
I hope the app looks interesting enough to you and, if it does, I hope it's also useful!
Cheers and happy new year 2018!