diff --git a/coinmanager/coinc/cache.py b/coinmanager/coinc/cache.py
new file mode 100644
index 0000000..92eeabd
--- /dev/null
+++ b/coinmanager/coinc/cache.py
@@ -0,0 +1,85 @@
+# encoding: utf-8
+#
+# Copyright (C) 2020 willipink.eu
+# Author Moritz Münch moritzmuench@mailbox.org
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+
+
+from hashlib import sha256
+from random import random
+
+from django.core.cache import cache
+from django.http import Http404
+
+#todo we dont need this, no db queries
+from .models import Coin
+from .models import Country
+
+
+def get_etag_index(request):
+    return cache.get(f'etag_index', set_etag_index())
+
+
+def get_last_modified_index(request):
+    return cache.get(f'last_modified_index', set_last_modified_index())
+
+
+def set_last_modified_index():
+    ''' set and return the datetime of the last coin added '''
+    try:
+        last_modified = Coin.objects.latest('date_modified').date_modified
+    except Coin.DoesNotExist:
+        raise Http404(f'Das Land "{name_iso}" existiert nicht')
+    cache.set(f'last_modified_index', last_modified)
+    return last_modified
+
+def get_last_modified_country(request, name_iso):
+    return cache.get(f'last_modified_{name_iso}', set_last_modified_country(name_iso))
+
+
+def set_last_modified_country(name_iso):
+    ''' return the datetime of the last coin added to a country '''
+    try:
+        last_modified = Coin.objects.filter(country=name_iso).latest('date_modified').date_modified
+    except Coin.DoesNotExist:
+        raise Http404(f'Das Land "{name_iso}" existiert nicht')
+    cache.set(f'last_modified_{name_iso}', last_modified)
+    return last_modified
+
+
+def set_etag_index():
+    etag = ''
+    for country in Country.objects.order_by('name_iso'):
+        etag += get_etag_country_(country.name_iso)
+    etag = sha256(etag.encode('utf-8')).hexdigest()[0:9]
+    cache.set(f'etag_index', etag)
+    return etag
+
+
+def get_etag_country_(name_iso):
+    return cache.get(f'etag_{name_iso}', set_etag_country(name_iso))
+
+
+def get_etag_country(request, name_iso):
+    return get_etag_country_(name_iso)
+
+
+def set_etag_country(name_iso):
+    print(name_iso, end='')
+    print(cache.get(f'etag_{name_iso}', f'error {name_iso}'))
+    etag = sha256(str(random()).encode('utf-8')).hexdigest()[0:9]
+    cache.set(f'etag_{name_iso}', etag)
+    return etag
diff --git a/coinmanager/coinc/helper.py b/coinmanager/coinc/helper.py
new file mode 100644
index 0000000..0d7aca4
--- /dev/null
+++ b/coinmanager/coinc/helper.py
@@ -0,0 +1,54 @@
+# encoding: utf-8
+#
+# Copyright (C) 2020 willipink.eu
+# Author Moritz Münch moritzmuench@mailbox.org
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+
+from .models import Country, Coin
+
+def total_coin_sum():
+    ''' add each coin_sum from each country and return the result
+    >>> total_coin_sum()
+    173.57
+    '''
+
+    total_coin_sum = 0
+    for country in Country.objects.order_by('name'):
+        total_coin_sum += coin_sum_of_(country)
+
+    return total_coin_sum
+
+
+def coin_sum_of_(country):
+    ''' calculate the sum of all coins from a country
+    >>> coin_sum_of_(germany)
+    346.82
+    '''
+
+    coin_count = {'total': 0}
+    for value in [1, 2, 5, 10, 20, 50, 100, 200, 201, 202, 203]:
+
+        coin_count[value] = Coin.objects.filter(
+                                country=country,
+                                value=value
+                            ).exclude(found_by__isnull=True).count()
+
+        if value > 200:
+            coin_count['total'] += 200 * coin_count[value]
+        else:
+            coin_count['total'] += value * coin_count[value]
+
+    return coin_count['total'] / 100