How to avoid too many (JOINS, SELECT, WHERE) to increase entity framework performance ?

int Shortages_StockNoSer = nDB01.stock_noserials
                .GroupBy(x => x.stitems_ID)
                .Select(grp => new
                {
                    itemID = grp.Key,
                    sum = grp.Sum(x => x.StockQnty),
                    min = grp.Select(s => 
                                     s.st_items.stitems_MinBalance).FirstOrDefault()
                }).Where(u => u.sum < u.min && u.min != 0)
                .Count();
int Shortages_StockWithSer = nDB01.purchases_item_seriels
               .GroupBy(x => x.stitems_ID)
               .Select(grp => new
               {
                   itemID = grp.Key,
                   sum = grp.Count(),
                   min = grp.Select(s => 
                                    s.st_items.stitems_MinBalance).FirstOrDefault()
               }).Where(u => u.sum < u.min && u.min != 0)
               .Count();
int CountShortagesItems = Convert.ToInt32( Shortages_StockNoSer) + 
                          Convert.ToInt32(Shortages_StockWithSer);

int CustomersBalances_StockNoSer = nDB01.people_data
                .GroupBy(x => x.pepole_ID)
                .Select(grp => new
                {
                    itemID = grp.Key,
                    balance = nDB01.account_items.Where(u => (u.account_main.accitem_PeplID == grp.Key && u.accitem_AccID == 10) ||
                                    (u.account_main.accitem_PeplID == grp.Key && u.accitem_AccID == 59)).FirstOrDefault().accitem_Debit -
                                    nDB01.account_items.Where(u => (u.account_main.accitem_PeplID == grp.Key && u.accitem_AccID == 10) ||
                                    (u.account_main.accitem_PeplID == grp.Key && u.accitem_AccID == 59)).FirstOrDefault().accitem_Credit,
                    Limited = grp.Select(s => s.pepole_CreditLimit).FirstOrDefault()
                }).Where(u => (u.balance) > u.Limited )
                .Count();